Nutrients

Sixteen chemical elements are known to be important to a plant’s growth and survival. The sixteen chemical elements are divided into two main groups: non-mineral and  mineral.  

Non-Mineral Nutrients

  • The Non-Mineral Nutrients are hydrogen (H), oxygen (O), & carbon (C).
  • These nutrients are found in the air and water. 
  • In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 – carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant’s food. 
  • Photosynthesis means “making things with light”.
  • Since plants get carbon, hydrogen, and oxygen from the air and water, there is little farmers and gardeners can do to control  how much of these nutrients a plant can use.

Mineral Nutrients

The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant’s roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many plumeria growers and gardeners use fertilizers to add the nutrients to the soil. The mineral nutrients are divided into two groups:
macronutrients and micronutrients.  

Macronutrients 

Macronutrients can be broken into two more groups: primary and secondary nutrients. 

The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.

The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.

Micronutrients

Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.

Soil

In general, most plants grow by absorbing nutrients from the soil. Their ability to do this depends on the nature of the soil. Depending on its location, a soil contains some combination of sand, silt, clay, and organic matter. The makeup of a soil (soil texture) and its acidity (pH) determine the extent to which nutrients are available to plants.

Soil Texture 

(the amount of sand, silt, clay, and organic matter in the soil)

Soil texture affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it. This condition is called leaching. When nutrients leach into the soil, they are not available for plants to use.

An ideal soil contains equivalent portions of sand, silt, clay, and organic matter. Soils across North Carolina vary in their texture and nutrient content, which makes some soils more productive than others. Sometimes, the nutrients that plants need occur naturally in the soil. Othertimes, they must be added to the soil as lime or fertilizer.

Soil pH

(a measure of the acidity or alkalinity of the soil) Soil pH is one of the most important soil properties that affects the availability of nutrients.

  • Macronutrients tend to be less available in soils with low pH.
  • Micronutrients tend to be less available in soils with high pH.

Lime – can be added to the soil to make it less sour (acid) and also supplies calcium and magnesium for plants to use. Lime also raises the pH to the desired range of 6.0 to 6.5.

In this pH range, nutrients are more readily available to plants, and microbial populations in the soil increase. Microbes convert nitrogen and sulfur to forms that plants can use. Lime also enhances the physical properties of the soil that promote water and air movement.

It is a good idea to have your soil tested. If you do, you will get a report that explains how much lime and fertilizer your crop needs.

Macronutrients

Nitrogen (N)

  • Nitrogen is a part of all living cells and is a necessary part of all proteins, enzymes and metabolic processes involved in the synthesis and transfer of energy.
  • Nitrogen is a part of chlorophyll, the green pigment of the plant that is responsible for photosynthesis. 
  • Helps plants with rapid growth, increasing seed and fruit production and improving the quality of leaf and forage crops. 
  • Nitrogen often comes from fertilizer application and from the air (legumes get their N from the atmosphere, water or rainfall contributes very little nitrogen)

Phosphorus (P)

  • Like nitrogen, phosphorus (P) is an essential part of the process of photosynthesis. 
  • Involved in the formation of all oils, sugars, starches, etc.
  • Helps with the transformation of solar energy into chemical energy; proper plant maturation; withstanding stress.
  • Effects rapid growth.
  • Encourages blooming and root growth.
  • Phosphorus often comes from fertilizer, bone meal, and superphosphate. 

Potassium (K)

  • Potassium is absorbed by plants in larger amounts than any other mineral element except nitrogen and, in some cases, calcium. 
  • Helps in the building of protein, photosynthesis, fruit quality and reduction of diseases.
  • Potassium is supplied to plants by soil minerals, organic materials, and fertilizer.

Calcium (Ca)

  • Calcium, an essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant. It is also thought to counteract the effect of alkali salts and organic acids within a plant. 
  • Sources of calcium are dolomitic lime, gypsum, and superphosphate.

Magnesium (Mg)

  • Magnesium is part of the chlorophyll in all green plants and essential for photosynthesis. It also helps activate many plant enzymes needed for growth.
  • Soil minerals, organic material, fertilizers, and dolomitic limestone are sources of magnesium for plants.

Sulfur (S)

  • Essential plant food for production of protein.
  • Promotes activity and development of enzymes and vitamins.
  • Helps in chlorophyll formation.
  • Improves root growth and seed production.
  • Helps with vigorous plant growth and resistance to cold.
  • Sulfur may be supplied to the soil from rainwater. It is also added in some fertilizers as an impurity, especially the lower grade fertilizers. The use of gypsum also increases soil sulfur levels. 

Micronutrients

Boron (B)

  • Helps in the use of nutrients and regulates other nutrients. 
  • Aids production of sugar and carbohydrates. 
  • Essential for seed and fruit development. 
  • Sources of boron are organic matter and borax

Copper (Cu)

  • Important for reproductive growth.
  • Aids in root metabolism and helps in the utilization of proteins. 

Chloride (Cl)

  • Aids plant metabolism. 
  • Chloride is found in the soil. 

Iron (Fe)

  • Essential for formation of chlorophyll.
  • Sources of iron are the soil, iron sulfate, iron chelate.

Manganese (Mn)

  • Functions with enzyme systems involved in breakdown of carbohydrates, and nitrogen metabolism. 
  • Soil is a source of manganese.

Molybdenum (Mo)

  • Helps in the use of nitrogen
  • Soil is a source of molybdenum. 

Zinc (Zn)

  • Essential for the transformation of carbohydrates.
  • Regulates consumption of sugars.
  • Part of the enzyme systems which regulate plant growth. 
  • Sources of zinc are soil, zinc oxide, zinc sulfate, zinc chelate.

Related Images:

Nitrogen deficiency guide

Nitrogen deficiency guide

Nitrogen is one of the important elements a plant needs. It is an important part of proteins, chlorophyll, vitamins, hormones and DNA. Because it is a component of enzymes, nitrogen is involved in all enzyme reactions and plays an active role in the plant’s metabolism. Nitrogen is mainly absorbed by the plant in the form of nitrate and ammonium. It can also be absorbed via small organic molecules.

It is important that the balance between nitrate and ammonium is correct in the feeding otherwise the pH in the rhizosphere (environment immediately surrounding the roots) will become too high or too low. Plants with nitrate as their source of nitrogen have a higher organic acid content. This has an influence on the taste and storage life of the harvest among other things.

Nitrate is converted into ammonium in the plant by the nitroreductase enzyme. Ammonium is then assimilated into organic molecules. Nitrogen has a positive influence on the plant’s growth. The plant gets bigger leaves, more branches and the vegetative period is extended.

About nitrogen in short

What is it and what does it do?
Nitrogen is a component of enzymes and is therefore involved in all enzyme reactions and plays an active role in the plant’s metabolism.
What can you see?
Purple stalks.
Yellowing leaves.
Leaves fall of.
What can you do?
Raise EC of the feeding or add extra nitrogen.

infocourier-nitro_text_4.jpg

Symptoms of a deficiency

Stalks will turn purple, quickly followed by larger leaves in the middle and top parts of the plant, leaves will turn more yellow and finally the leaves whither and fall off.

Development of a deficiency

  • The plant is a lighter color as a whole.
  • Larger leaves in the lower part of the plant turn light green. The leaf stalks of the smaller leaves now also turn purple. Typical vertical purple stripes appear in the stem.
  • Leaves in the lower part of the plant turn more yellow and then become white.
  • The growth is visibly inhibited giving shorter plants, thinner stems, less leaf formation and smaller leaves.
  • Further yellowing and whitening occurs in the top and middle parts of the plant.
  • Leaves on growing points remain green longer but they are a lot less green than at normal nitrogen levels.
  • Forced flowering starts and there is substantial leaf loss. Substantial reduction in yield.

infocourier-nitro_text_3.jpg

Reasons for a deficiency

Deficiency can be caused by incorrect feeding or giving feeding that contains insufficient nutrient elements. Substrates that contain a lot of fresh organic material can cause nitrogen deficiency because micro-organisms bind the nitrogen. A lot of nitrogen can be bound, particularly in the first weeks; this is released later but it is generally too late.

Solutions to resolve a deficiency

Raise the EC of the feeding and rinse the substrate well with it.

  • Add nitrogen yourself to the feeding solution by using urea, blood meal, semi-liquid manure or by using a special “mono-nutrient’ product.
  • Spray the underside of the leaves with a nitrogen solution. This can best be done at the end of the day, just before the lights are turned off. Be careful not to cause burning.

Related Images:

Soils and Growing Mediums

What Is Soil?

Soil is a living, breathing, natural entity composed of solids, liquids, and gases.

Soil has five major functions:

  1. Provides a habitat for organisms
  2. Recycles waste products
  3. Filters water
  4. Serves as an engineering material
  5. Provides a medium for plumeria growth

Our focus will be on the fifth function. In this role, soil provides structural stability for plumeria and retains and relinquishes water and the nutrients necessary for plumeria growth.

An ideal soil for plant growth contains 50% porespace and 50% solids, with the porespace filled with equal parts air and water. This distribution rarely occurs because porespace varies with soil texture and soil management. For example, tilling increases porespace, while poor drainage and compaction reduce it.

Soil solids are a blend of mineral materials and organic matter. The mineral materials are typically weathered rock of varying sizes called sand, silt, and clay. The organic matter consists of decaying plant and microbial residues. The relative amounts of porespace and mineral and organic matter vary greatly among different soil types. But for plumeria growth, most soil scientists agree that 50% porespace, 45% mineral matter, and 5% organic matter make up an ideal ratio. The distribution of soils and porespace in compacted in poorly drained soil.

Even a small amount of organic matter can have a dramatic effect on the physical, chemical, and biological properties of soil.

1Brady, N. C. and R. R. Weil. 2004. Elements of the Nature and Properties of Soils, 2nd Edition. Atlanta, GA: Prentice Hall.

The Soil Profile

Most naturally occurring, undisturbed soils have three distinct layers of variable thicknesses. The layers are the topsoil, subsoil, and parent material. Each layer can have two or more sublayers called horizons. Collectively, the horizons make up the soil profile. The predominate parent material varies by location.

Soils’ properties vary with the soil depth. The surface soil, or topsoil layer (O and A horizon in Figure 1–2), usually contains less clay, but more organic matter and air, than the lower soil layers. Topsoil is usually more fertile than the other layers and has the greatest concentration of plant roots.

The subsurface layer (B and C horizon in Figure 1–2), known as subsoil, usually has a higher clay content and lower organic matter content than the topsoil.

Soil properties often limit the depth to which plant roots can penetrate. For example, roots will not grow through an impenetrable layer. That layer may be bedrock (Figure 1–3), compacted soil, or a chemical barrier, such as an acidic (very low) pH. A high water table can also restrict root growth due to poor soil aeration. Few big trees grow in shallow soils because big trees are unable to develop a root system strong enough to prevent them from toppling over. Shallow soils also tend to be more drought-prone because they hold less water and thus dry out faster than deeper soils. Water lost to runoff on shallow soils would instead be absorbed by a deeper soil. In addition, deep soils allow the roots to explore a greater volume, which means the roots can retain more water and plant nutrients.

Soils change in three dimensions. The first dimension is from the top to the bottom of the soil profile. The other two dimensions are north to south and east to west. The practical meaning of this three-dimensional variability is that as you move across a state, a county, or even a field, the soils change.

Five factors of soil formation account for this variation:

  1. Parent material
  2. Biological activity
  3. Climate
  4. Topography
  5. Time

Differences in even one of these factors will result in a different soil type. Soils forming from different parent materials differ. Soils forming from the same parent material in varying climates differ. Soils at the top of a hill differ from soils at the bottom. The top of the hill loses material due to natural erosion; the bottom gains the material from above. Considering the number of possible combinations of these five factors, it is not surprising that more than 450 unique soil series are currently mapped in North Carolina. Globally, more than 20,000 different soil series occur.

soil-horizon

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Physical Properties of Soil

The physical properties of soil are characteristics that can be seen, felt, or measured. These include color, texture, structure, and water-holding capacity. Such properties usually determine the suitability of soil as a growth medium. Some physical properties, such as texture, are not economically feasible to change on a large scale.

A soil’s fertility, which is a chemical property, is easier to change than the soil’s physical properties.


Color

Organic matter, the soil minerals present, and the drainage conditions all influence soil color. Color alone is not an indicator of soil quality, but color does provide clues about certain conditions. For example, light or pale colors in grainy topsoil are frequently associated with low organic matter content, high sand content, and excessive leaching. Dark soil colors may result from poor drainage or high organic matter content. Shades of red indicate a clay soil is well-aerated, while shades of gray indicate inadequate drainage (Figure 1–4). In well-drained soils of the NC mountains and piedmont, the subsoil colors are often shades of red, brown, and yellow. In poorly drained soils, the subsoil is grayer in color.

Texture

Soil texture, which refers to the proportions of sand, silt, and clay, influences nearly every aspect of soil use and management. Sand is the largest particle (at 2.0 to 0.05 mm), silt is much smaller (0.05 to 0.002 mm), and clay is the smallest (less than 0.002 mm) (Figure 1–5). To compare particle sizes, imagine that a sand particle is the size of a basketball. On that scale, a silt particle would be the size of a marble, and a particle of clay would be a pinpoint. How fine (clayey) or coarse (sandy) a soil is will determine many of the soil’s physical and chemical properties.

Much of a soil particle’s ability to react with water and nutrients is related to the amount of surface area available. When the individual particle size is small, more individual particles will fit in a given space, and thus make more surface area available. Clay, with its tiny particle size and platelike structure, holds water and nutrients effectively, while sand, which has a large chunky structure, does not. In addition to being smaller, clay particles are composed of different minerals than sand and silt, and a clay particle’s structure is more like a stack of paper plates than a grain of sand (Figure 1–6).

Table 11. Particle type, number of particles per gram, and the average surface area per gram.

Particle TypeDiameter (mm)Number of Particles per gramSpecific surface area (cm2/g)
Clay< 0.00290,260,853,0008,000,000
Coarse sand1.00-0.5072023
Fine sand0.25-0.1046,00091
Medium sand0.50-0.255,70045
Silt0.05-0.0025,776,000454
Very coarse sand2.00-1.009011
Very fine sand0.10-0.05722,000227

Rocks and Gravel

Rocks and gravel, which are large, coarse materials, can be found in many soils, but they are not considered when determining soil texture. Although some rocks and gravel in the soil will not affect plant nutrient uptake, they can make the soil difficult to dig. If the garden is mostly rocks or gravel, the soil will have a reduced water- and nutrient-holding capacity, and will be unfit for growing plants. In such a situation, it may be easiest to install raised beds and import soil.

The relative proportions of sand, silt, and clay determine a soil’s textural class (Figure 1–7). For example, a soil that is 12% sand, 55% clay, and 33% silt is in the clay textural class. Soil texture is a permanent feature, not easily changed by human activity. Consider a typical mineral soil that is 6 inches deep on 1 acre. That soil weighs about 2 million pounds. To change the sand content just 1% would require adding 20,000 pounds (or 10 tons) of sand. A 1% change in sand content would have minimal effect. A significant effect might require a 10% change, which would mean adding 100 tons of sand.

Adding organic matter is a more economically feasible alternative for improving soil. Adding organic matter does not change a soil’s texture—the percentage of sand, silt, and clay in the soil—but adding organic matter will alter soil structure by increasing the porespace and improving drainage. Gardeners can be successful with any soil texture, as long as they know the attributes and limitations of that soil.

Typically, laboratory procedures are used to determine the soil texture. It is possible, however, to use the procedure outlined in Figure 1–8 to determine the textural class by the “feel” method. It takes practice and calibration, but it can provide a reasonable estimate of the soil texture.

Sandy or Coarsely Textured Soils (Figure 1–9)

  • Low in organic matter content and native fertility.
  • Rapidly permeable and do not hold soil moisture.
  • Nutrient leaching is a concern, so proper fertilization is a must. Apply smaller amounts of nutrients, and apply them more frequently.
  • Low in cation exchange and buffer capacities.
  • Well-suited for road foundations and building sites.
  • Feel gritty.

Loamy or Medium-Textured Soils (Figure 1–10)

  • Contains more organic matter.
  • Permit slower movement of water and are better able to retain moisture and nutrients.
  • Are generally more fertile.
  • Have higher cation exchange and buffer capacities.
  • Feel crumbly.

Clayey or Finely Textured Soils (Figure 1–11)

  • Higher nutrient-holding capacity.
  • Higher available water-holding capacity.
  • Finely textured soils exhibit properties that are somewhat difficult to manage or overcome.
  • Often too sticky when wet and too hard when dry to cultivate.
  • May have shrink-and-swell characteristics that affect construction uses.
  • Feel slippery.

How Do Soil Types Affect Gardeners?

Compaction. Compaction occurs when pressure is applied to soil particles and the air and water are pushed out of the porespaces. Large, cubic sand particles are not easily compacted. Clay particles, small and platelike, are easily aligned and can compact, especially when wet. Compaction inhibits the movement of water, gases (air), and roots. Compacted soils have less infiltration, greater runoff, a higher risk of erosion, and more restricted root growth than soils without compaction. Water drains slowly, which may increase the likelihood of plant root diseases.

Erosion. Sand particles are heavy, so they are not easily picked up and moved by water or wind. Clay particles are sticky, so they are not easily moved. Silty loam particles are light and not sticky, so erosive forces easily move them. Eroded soils are usually harder to till and have lower productivity than soils without erosion. The main causes of soil erosion in North Carolina are insufficient vegetative or mulch cover, and improper equipment and methods used to prepare and till the soil (Figure 1–12).

Soil erosion can be minimized by following a few preventive measures:

  • Choose plants suited to the soil so they establish well.
  • Mulch the surface each year with organic materials 1 inch to 3 inches deep.
  • Adequately fertilize to promote vigorous, but not excessive, plant growth.
  • Create a water diversion, such as a grass waterway, to capture and slow water movement.
  • Align rows to follow the land’s contour so that water flowing downhill is slowed.
  • Use proper tillage methods, such as not tilling when the soil is overly wet and not overtilling.
  • Plant a winter cover crop.
  • Consider installing rain gardens to capture sediment and runoff.

Surface Area. The most active part of a soil particle is its surface area. A particle’s surface is where nutrient exchange takes place. Sand particles have a small surface area relative to their mass, meaning they do not hold onto nutrients well. Clay particles have a large surface area relative to their mass, so a small amount of clay can add a significant amount of surface area to a soil, increasing the nutrient-holding capacity.

Structure

Soil structure refers to the grouping of individual soil particles into larger pieces called peds or aggregates. The structure of topsoil is usually granular and resembles chocolate cookie crumbs (Figure 1–13). Good granular structure allows rapid movement of air and water within the soil. Poor granular structure decreases movement of air and water. Good soil structure allows for extensive root development; poor structure can limit root growth. Supplying an adequate amount of organic matter and working the soil only when it is not excessively wet promotes good topsoil structure.

Water-Holding Capacity

Water enters the soil from precipitation or irrigation. It exits by draining from the soil, evaporating from the surface, and through transpiration from plant leaves. Water-holding capacity—the retention of water moving through soil—depends on differences in soil porespace. Ideal soils are half porespace with equal amounts of air and water filling the pores. Too much air means plants will wilt. Too much water means reduced plant vigor and susceptibility to root rot, which occurs due to anaerobic conditions.

Soils differ in the number of large (macro), medium (meso), and small (micro) pores. Macropores, which are more common in sandy soils, take up water more quickly and drain faster than meso- and micropores. This rapid draining from macropores is called “gravitational water” because the weaker forces of adhesion and cohesion in macropores cannot overcome gravity’s pull. Within 24 hours after a saturating rain, gravitational water reaches the lower soil horizons, and the soil is at field capacity: the meso- and micropores are still full of water because their adhesive and cohesive forces are stronger than gravity. Water in the mesopores is available to plants. But when the mesopores lose water as the soil dries through plant uptake and transpiration, soil moisture reaches the permanent wilting point. At the permanent wilting point, micropores are still full of water, but this water is so tightly held that it is not plant-available. Note that plants may wilt before the permanent wilting point if the plant transpires water through the leaves faster than it can take water up from the soil through its roots. This is why plants may wilt on hot days and then recover once the sun goes down and why plants can balance uptake with transpiration (Figure 1–14).

How to Remediate Compaction

Compaction is a likely problem if there has been recent construction or other traffic over the area. Deep cultivation, which is mixing the top 6 inches to 2 feet of soil with a tiller, disk, or hand tools, may be needed to loosen the soil. Incorporation of organic matter during deep cultivation can help to rehabilitate soil structure by creating aggregates and both macropores (for drainage) and mesopores (for plant-available water). Digging or cultivating soil when it is wet or excessively dry can destroy structure.

Be wary of quick fixes, such as starting over with a truckload of topsoil. Unfortunately, there are no standards on material sold as “topsoil.” New problems may be brought on site, such as weed seeds and disease organisms. Adding new topsoil to existing soil may also create drainage problems when water moves through the purchased topsoil and reaches the compacted layer. The water can pool and create unfavorable conditions for root growth.

Clay soils, which tend to hold excessive amounts of water and become compacted easily, present some tricky problems. Common mistakes are adding sand or peat moss to improve drainage. Adding sand to clay will reduce soil structure, lowering porespace. Adding peat moss will increase the clay soil’s high moisture-holding capacity. The best advice is to add smaller amounts of organic matter consistently every year, minimize compaction, and let soil biology naturally improve the structure over time.

Organic Matter

Organic matter consists of the remains of plants and animals and gives soil a gray to very-dark-brown color. Organic matter is home to many soil organisms.

Earthworms, insects, bacteria, fungi, and animals use organic matter as food, breaking it down to obtain energy and essential nutrients. Humus is the portion of organic matter that remains after most decomposition has taken place (Figure 1–16).

When organic matter decomposes in the soil, carbon dioxide is released and replaces some of the oxygen in soil pores. Carbon dioxide is dissolved by water in soil to form a weak acid. This solution reacts with soil minerals to release nutrients that can be taken up by plants. The digested and decomposing organic matter also helps develop good air-water relationships. In sandy soil, organic material occupies some of the space between the sand grains. This binds them together and increases water-holding capacity. In a finely textured or clay soil, organic material creates aggregates of soil particles. This allows water to move more rapidly around soil particles.

The amount of organic matter in the soil depends primarily on rainfall, air temperature, the kinds of plants that have been growing in a soil, management practices, soil temperature, and drainage. Soils that are tilled frequently are usually low in organic matter because tilling decreases residue particle size and increases the amount of air in the soil, increasing the rate of organic matter decomposition. Poorly drained soils tend to have a high percentage of organic matter because low oxygen levels limit decomposition organisms. To build organic matter in garden soil, till in compost when the garden is first created, but do not till in subsequent years. Instead, apply thin layers (1 inch to 3 inches), of organic mulch or compost to the soil surface each year (Figure 1–17). This material will break down, and the organic matter levels in the soil will gradually increase.

Improving the Soil

Good aeration and drainage, as well as the ability to hold adequate moisture and nutrients, are key components of an ideal soil environment. Although there is no cookbook recipe for creating this ideal environment, these are some of the most important strategies for improving soil quality:

  • Minimize soil compaction (do not walk on garden beds or work wet soil) (Figure 1–18).
  • Reduce drainage problems.
  • Decrease erosion.
  • Plant a cover crop (Figure 1–19).
  • Incorporate organic matter.
  • Provide a 1- to 3-inch layer of organic mulch on the soil’s surface.

Organic amendments can improve soils that suffer from high compaction, poor drainage, and erosion. Materials such as compost, manures, and pine bark are more effective and economical than vermiculite, peat moss, sand, topsoil, or perlite. Table 1–2 reviews the amounts of organic material to be added to soil per 100 square feet. When working in small areas, a general rule of thumb is to incorporate a 3- to 6-inch layer of organic material into the soil. The organic matter must be decomposed before plants can use the nutrients. The rate of decomposition of organic matter by soil organisms is affected by moisture, temperature, particle size, the carbon-to-nitrogen ratio, and nitrogen availability. The proper balance of carbon and nitrogen is needed for rapid decomposition, as are warm temperatures and adequate moisture. When using straw, leaves, or sawdust (which are high in carbon), add nitrogen fertilizer while the material is decomposing. Soil microbes use nitrogen during decomposition and may deprive plants, resulting in slow or stunted plant growth. Incorporating organic matter some months before planting the garden allows the material time to decompose and have plant-available nutrients in place for good plant growth.

Table 1–2. Organic Materials and Their Application Rates

Organic MaterialAmount to Be Added per 100 Square Feet
Compost10–20 cubic feet
Corncobs50 pounds (2 bushels)
Hay60 pounds (1 bale)
Leaves75 pounds (3–4 bushels)
Sawdust50 pounds (2 bushels)
Straw60 pounds (1 bale)
Wood chips50 pounds (2 bushels)

Incorporating Soil Amendments

Conditioning soil requires increasing organic matter content to 25% by volume. Incorporating a minimum of 2 inches of material into the top 6 inches of soil will create approximately 8 inches of amended soil. These additions raise the planting bed, improving drainage and making plants more visible. Incorporating more than 50% organic matter may negatively affect plant growth. Be careful when using organic material, making certain that it is fully composted and not merely aged. Microbes attracted to partially decomposed materials will compete with plants for nutrients, especially nitrogen and sulfur, resulting in nutrient deficiencies and poor plant growth.

The best organic matter amendments for clay soils are pine bark (less than 1/2 inch in diameter) and composted leaf mold. The following amendments are not recommended because they do not adequately improve the physical properties of clay soil: peat moss, sand, hardwood bark, wood chips, and pine straw.

For sandy soils, organic matter amendments, such as pine bark or compost, will improve water retention.

Figure 1–19. A cover crop of white rye grass was planted in this annual flower bed. It is being turned under to add nutrients to the soil before planting.

Chemical Properties of Soil

There are strong relationships between soil physical properties and soil chemical properties. For example, surface area is directly related to chemical reactivity.

Cation Exchange Capacity (CEC)

The negative ends of two magnets repel each other. The negative end of one magnet attracts the positive end of another magnet. This same principle affects the retention of plant nutrients in soil. Some plant nutrients are cations, which have a positive charge, and some are anions, which have a negative charge. Just like the opposite poles on magnets, cations will be attracted to anions.

Soil particles are similar to a magnet, attracting and retaining oppositely charged ions and holding them against the downward movement of water through the soil profile. The nutrients held by the soil in this manner are called “exchangeable cations” and can be displaced or exchanged only by other cations that take their place. Thus, the negative charge on a soil is called the cation exchange capacity (CEC). Soils with high CEC not only hold more nutrients, they are better able to buffer or avoid rapid changes in the soil solution levels of these nutrients. A soil test will tell you the CEC number of your soil. Soils high in clay, silt, or organic matter will have a CEC number of 10 or greater, and no remediation is needed. Sandy soils will have a CEC number between 1 and 5. Adding organic matter to these soils will help increase the CEC.

Too Much of a Good Thing: Nitrogen Leaching

Soil testing provides valuable information on pH and plant-available nutrients. Test your soil before planting and every two to three years thereafter. Inexpensive soil test kits are unreliable. To accurately determine your soil characteristics and the proper amount of lime and fertilizer to apply, contact the NC Department of Agriculture and Consumer Services (NCDA&CS). The accuracy of these reports, however, depends on the quality of the sample submitted.

Soil Testing Just like magnets, negative charges repel negative charges. Soils with high CEC tend not to hold anions. As a result, water moving through the soil profile will leach negatively charged nutrients, such as chloride, nitrate, and sulfate out of the root zone. This leaching can result in contamination of groundwater, streams, and lakes or have other environmental implications (Figure 1–20). Excess fertilizer becomes a contaminant and can have adverse effects on human health. The U.S. Environmental Protection Agency has set standards for nutrients in groundwater used for drinking water. This is one of many reasons that appropriate levels of fertilization are essential.

Tips for Collecting a Good Soil Sample

  • Collect samples with stainless steel or chrome-plated tools. Using brass, bronze, or galvanized materials could contaminate the sample.
  • The bucket in which material is collected should be made of plastic.
  • Make sure the collection bucket is clean because even small amounts of residual lime or fertilizer can affect the test results.
  • Avoid taking samples from areas that are obviously different from the norm, such as wet spots, compost piles, animal urine spots, and brush piles, or from under eaves or sites where trash has been burned.
  • Remove large pieces of organic material, such as roots, stalks, and leaves, from the sample.
  • For gardens, new lawns, and other cultivated areas, sample to the depth the soil has been, or will be, tilled. For established lawns, collect the sample 2 to 4 inches deep. For trees and shrubs, take a sample to a depth of 6 inches near the plant’s drip line. Even if the soil looks the same, take separate samples for flower beds, vegetable gardens, fruit orchards, shrub borders, and lawn areas.
  • If using a trowel or spade, dig a hole, then take a slice of soil down one side. Repeat this procedure in five to eight spots for each area to be tested. Mix these cores together to obtain one composite sample. If the soil is very wet, it could be more difficult to mix, but do not attempt to heat the soil to dry it (Figure 1–21).
  • Place about a pint of the composite sample for each area sampled in a soil testing box and label with a return address on the side of the box. Make up a code that will be easy to remember, such as “flawn” for front lawn, “byard” for back yard, or “veg” for vegetable garden. Any combination of letters and numbers can be used. Make notes about where the samples came from so that when you receive the results, you can easily Identify how to treat the areas differently based on the results.
  • Do not tape the boxes in any way. The lids are removed before the boxes go in the soil lab ovens, and tape makes this process difficult. Do not put the soil in a plastic bag before placing it in the box as doing so will prevent proper drying in the lab oven.

Fill out the soil test report sheet, giving as much information as possible. The required items are name, address, county, sample codes, and the crops planned. Reports are sent by mail only if there is a special request submitted to the lab. Otherwise, provide an email address on the form to receive notification that the report is complete and online. Farmers also use the form, so some of the information requested may not apply to gardeners (pounds of lime per acre, for example). Forms and boxes are available from the NCDA & CS or any county Cooperative Extension center.

Learn more about collecting soil samples in SoilFacts: Careful Soil Sampling—The Key to Reliable Soil Test Information (NC Cooperative Extension publication number AG-439-30). For detailed information about the soil test results, refer to NCDA&CS Agronomic Division’s Understanding the Soil Test Report.

How to Use a Soil Test Report

Fertilizing trees and shrubs in a landscape should be based on the amount of rainfall, soil type, the plant’s age, the amount of current growth, and desired future growth. Over application of fertilizer to home landscapes wastes money, contributes to pollution in our rivers, streams, lakes and estuaries, and may damage or kill desired plants. In addition, excess fertilizer can increase the likelihood of disease problems, lead to weak growth, attract pests, and increase the amount of pruning to keep mature plants within appropriate boundaries. A soil test report provides accurate guidance for applying fertilizer.

Example Soil Test Reports

Depending on the crop indicated when the soil sample was submitted, the soil test report provides results in one of two ways:

  • Home garden scale: Recommendations for pounds of lime and a rate and grade of fertilizer per 1,000 square feet (for example, an area 50 feet by 20 feet or 10 feet by 100 feet).
  • Farm/Forest scale: Recommendations for tons of lime and a rate and grade of fertilizer per acre.

At the home gardener scale:

  1. Measure the area to be limed or fertilized.
  2. Multiply the length by the width to determine the number of square feet.
  3. Divide by 1,000 to obtain the number of units to be treated.
  4. Multiply the number of units by the pounds of material to treat 1,000 square feet. This calculation will give the amount of fertilizer and lime needed (Figure 1–23).

Example 1:
If the area is 500 feet by 20 feet, and the suggested lime or fertilizer treatment is 30 pounds per 1,000 square feet:

  1. 500 × 20 = 10,000 square feet
  2. Divide 10,000 by 1,000 = 10 units
  3. Multiply 30 pounds times 10 units = 300 pounds of material (fertilizer or lime) per 10,000 square feet

Example 2:
If the area is 10 feet by 15 feet, and the suggested lime or fertilizer rate is 10 pounds per 1,000 square feet:

  1. 10 × 15 = 150 square feet
  2. Divide 150 by 1,000 = 0.15
  3. Multiply 10 pounds times 0.15 units = 1.5 pounds of material per 150 square feet

Or, look at fertilizer/lime calculations as ratios:

If 5 pounds of fertilizer are applied per 1,000 square feet, how many pounds should be applied to 150 square feet (using the garden size in Example 2)?< /p>

5 lb/1,000 sq ft = X lb/150 sq ft

5 lb × 150 sq ft /1,000 sq ft = X lb

750/1,000 = .75 lb

Example soil test reports and their recommended fertilizer applications can be found in Figure 1–24, Figure 1–25, Figure 1–26, and Figure 1–27.

Soil pH

Soil pH is a measure of the soil’s relative acidity or basicity. The pH scale ranges from 0 to 14. A pH of 7 is a neutral state, representing the value found in pure water. Values above 7.0 are basic, while values below 7.0 are acidic. The pH scale is logarithmic, meaning each unit has a 10-fold increase of acidity or basicity. Thus, compared to a pH of 7.0, a pH of 6.0 is ten times more acidic, and a pH of 5.0 is 100 times more acidic.

Nutrient Availability and pH

The optimum pH for a plant varies with organic matter content and plant type. Plant nutrient availability is strongly tied to the pH in the soil solution (Figure 1–28). Decreasing soil pH directly increases the solubility of the plant nutrients manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe). Acidic soils make these nutrients more available. At pH values less than about 5.5, toxic levels of Mn, Zn, or aluminum (Al), a non-nutrient element very common in our southern soils, may be released. The impact of pH on nutrient availability is very important—both for maximum plant availability and to avoid potentially toxic levels at very low or very high pH.

The optimal pH for growth differs among plants. For example, regardless of organic matter content, azaleas and blueberries are well-suited for a soil pH of about 5.0. In contrast, asparagus can tolerate a basic soil with a pH up to 8.0. A soil pH of 6.5 to 7.0 is often considered “ideal” for most plants, but a little research can help you identify the proper pH for the plants you wish to grow. After obtaining a soil test report, you can take measures to adjust soil pH or select plants that will thrive at the current pH. Extreme pH measures of 4.0 (acidic) or 10.0 (basic) will support little plant life and are very difficult to modify.

Adjusting pH

If the soil pH is too basic for the desired plant, incorporating an acidic soil amendment such as pine bark or compost, or applying elemental sulfur, will lower soil pH. Apply sulfur with caution; too much can harm plants.

If the soil pH is too acidic, apply lime to raise the soil pH. There are two general classes of liming materials: calcitic (without magnesium) and dolomitic (with magnesium). Calcitic lime is composed of calcium carbonate (CaCO3) and can be used on soils high in magnesium. Dolomitic lime is a mixture of calcium and magnesium carbonates (CaCO3 and MgCO3), which is the preferred liming material for soils low in magnesium.

Knowing the soil type or even the current pH is not enough to determine the amount of lime needed. The texture of the soil, organic matter content, crop to be grown, target pH, level of soil acidity, CEC, type and amount of clay, and the current pH are all factors to consider in adjusting pH. Soils low in organic matter or high in sand content require less lime to change the pH than clay soils or those with high organic matter.

Lime is heavily regulated in North Carolina. Lime must be labeled with a guarantee of percent calcium and magnesium. The percent of calcium carbonate equivalent also must be included on the label, as well as the pounds of material that equal 1 ton of standard lime (Figure 1–29). Each type of lime must meet a screening requirement for particle size. Lime pellets are formed from lime that has been finely ground. The pelleted product is less dusty and easier to apply, but is slower to react with the soil.

Lime moves slowly in the soil and neutralizes acidity only in the area where it is applied. To be effective, it should be spread and thoroughly incorporated. It takes several months for lime to react in the soil, which is why it is good to soil test and plan for proper soil pH management. For established lawns, gardens, and ornamentals that require lime, apply the recommended amount up to 50 pounds of lime per 1,000 square feet in one application to the soil’s surface. For recommended rates over 50 pounds, wait several months to make a repeat application to avoid a surface buildup of lime. For new plantings where the area will be tilled, apply the entire recommended amount at one time.

Learn more in SoilFacts: Soil Acidity and Liming: Basic Information for Farmers and Gardeners.

soil-sample-dwight-sipler-ccby20

Plant Nutrition and Fertilization

Many people confuse plant nutrition with fertilization. Plant nutrition refers to the needs of the plant and how a plant uses the basic chemical elements. Fertilization is the term used when these elements are supplied to the soil as amendments. Adding fertilizer during unfavorable growing conditions will not enhance plant growth and may actually harm or kill plants.

To complete their life cycle, plants need 17 essential nutrients, each in varying amounts (Table 1–3). Of these nutrients, three are found in air and water: carbon (C), hydrogen (H), and oxygen (O). Combined, C, H, and O account for about 94% of a plant’s weight. The other 6% of a plant’s weight includes the remaining 14 nutrients, all of which must come from the soil. Of these, nitrogen (N), phosphorus (P), and potassium (K), the primary macronutrients, are the most needed. Magnesium (Mg), calcium (Ca), and sulfur (S), the secondary macronutrients, are next in the amount needed. The eight other elements—boron, chlorine, copper, iron, manganese, molybdenum, nickel, and zinc—are called micronutrients because they are needed in much smaller amounts than the macronutrients.

Table 1–3. Relative Amounts (out of 100) of the Essential Nutrients Required by Most Plants

Primary Nutrients

Carbon (C)45
Oxygen (O)45
Hydrogen (H)6
Nitrogen (N)1.5
Potassium (K)1
Phosphorus (P)0.2

Secondary Nutrients

Calcium (Ca)0.5
Magnesium (Mg)0.2
Sulfur (S)0.1

Micronutrients

Iron (Fe)0.01
Chlorine (Cl)0.01
Manganese (Mn)0.005
Boron (B)0.002
Zinc (Zn)0.002
Copper (Cu)0.0006
Molybdenum (Mo)0.00001
Amounts unknown for Nickel (Ni) and Cobalt (Co)


Soil Nutrients

For a plant to absorb an element, it must be in a chemical form used by the plant and dissolved in the soil water. In addition to those nutrients already dissolved in soil water, nutrients can be present in the soil in these forms:

  • Undissolved or granular form, as from newly applied fertilizer
  • Chemicals bound to soil particles
  • The chemical structure of soil organic matter released by microbial decomposition

Undissolved or granular nutrients, and those that are chemically bound to soil particles, are not immediately useful, although they have the potential to benefit the plant. For many plant nutrients, the soil acts as a bank. Withdrawals are made from the soil solution, much as you would withdraw money from a checking account. The undissolved pool of soil nutrients is like a savings account. When checking funds are low, transfers are made from the savings account to the checking account. When a checking account is flush with money, some can be moved to savings for long-term retention. In the same way, for many plant nutrients, when the soil solution has excess nutrients, some bind to the soil to become temporarily unavailable, and some react with other chemical elements to form insoluble minerals, which can dissolve again later.

Several factors improve a plant’s ability to use nutrients:

  • Type of soil: The more clay and organic matter a soil has, the higher its CEC will be, and the more cationic (positively charged) nutrients it will retain.
  • Soil pH: The pH affects how tightly nutrients are bound to soil particles. If the soil pH is extremely high (basic) or very low (acidic), many nutrients become inaccessible to the plant because they are no longer dissolved in the soil water.
  • Types of nutrients in the soil: Some nutrients affect the availability of other nutrients. In fact, an apparent deficiency of one nutrient may actually be caused by a large amount of another.
  • Amount of soil water: Too much rain leaches nutrients from the soil. If there is too little water, the nutrients cannot dissolve and move into the plant.
  • Anything that affects the plant’s growth: If growing conditions are good, a plant will absorb nutrients from the soil. If the plant experiences extremes in temperature, incorrect light levels, or waterlogged or compacted soil, it will have a limited ability to absorb nutrients. Also, plants in dormant stages absorb few nutrients.

The presence or absence of nutrients can cause outward symptoms to appear on the plant. Table 1–4 reviews the essential nutrients for plant growth and symptoms that may appear if a plant is suffering a deficency or an excess of that nutrient.

Fertilizers

Fertilizers provide some elements that might be lacking in the soil and stimulate healthy, vigorous growth. How much and when to apply fertilizers should be based on observing plant performance, a reliable soil test, and an understanding of the factors that affect growth: light, water, temperature, pests, and nutrition. Simply applying fertilizer because a plant is not growing adequately will not solve many plant problems (insects, disease, or poor drainage, for example), and, in fact, excess nitrogen can often increase insect and disease infestation.

All fertilizers are labeled with three numbers, giving the percentage (by weight) of nitrogen (N), phosphorus (P), and potassium (K). This is referred to as the fertilizer grade.

A 100-pound bag of fertilizer labeled 0-20-10 has 0 pounds of N, 20 pounds of P (reported as P2O5), 10 pounds of K (reported as K2O), and 70 pounds of filler. Filler is added to make the fertilizer easier to spread and to reduce the likelihood of burning plants with too much fertilizer (the fertilizer salts can pull water out of the plant). A fertilizer may also contain secondary macronutrients or micronutrients not listed on the label because the manufacturer does not want to guarantee their exact amounts.

Fertilizers can be divided into two broad categories: natural and synthetic.

Natural fertilizers are commonly misnamed “organic.” “Natural fertilizers” is a more accurate description because these materials can be both complex chemical substances containing carbon (organic materials) or inorganic ores, such as rock phosphate, which are mined. Natural fertilizers containing organic materials include manures and composts, animal byproducts (such as bone meal, blood meal, feather meal), and seed meals. Natural fertilizers that are inorganic ores include potassium and lime.

Natural fertilizers typically release nutrients at a slower rate and over a longer period than synthetic fertilizers because microorganisms are involved in a breakdown and release cycle called mineralization. Moisture, temperature, and the microbial species and populations in the soil affect mineralization. Some water-soluble natural fertilizers, such as fish emulsion, are available when rapid nutrient delivery is desired.

When using natural fertilizers, it is helpful to incorporate them and provide adequate moisture for active microbial populations. When packaged as fertilizers, natural fertilizers will have the nutrient analysis stated on the labels. How much to use varies with the nutrient content of the material. The age of the material is also a factor. Producers are not required by law to state the nutrient content on bulk organic materials, such as compost, manure, and sludges. The source of these materials should be investigated and possible analysis performed at the Plant, Waste, Solution, and Media Lab at the NCDA&CS Agronomic Division before applying large amounts to a home garden.

The age of the natural fertilizers is another important factor. When natural material decays and is rained on, it loses nutrients, especially potassium and, to some extent, nitrogen. Even natural sources of nutrients can be overappled and damage plants. Fresh manures, for example, may injure plants by adding excessive nitrogen or potassium, especially when applied in large quantities.

Natural fertilizers can be expensive if applied in amounts adequate to supply nutrients for good plant growth, but have the added benefit of improving soil structure and plant vigor. When applying natural fertilizers, calculate as closely as possible the amounts of nutrients being supplied. Always err on the low side of application rates, then test the soil and augment as recommended on the soil test report. The nutrient content may need to be supplemented with other natural or synthetic materials to achieve a balanced ration of nutrients.

Synthetic fertilizers are made through industrial processes or mined from deposits in the earth. They are purified, mixed, blended, and altered for easy handling and application. Most are noncarbonaceous chemicals from nonliving sources and are usually cheaper than natural fertilizers. In general, nutrients are more rapidly available to plants because they are more water-soluble or in a form plants can use. The disadvantage is that it may be easier to over apply a synthetic fertilizer than a natural one, which may result in fertilizer burn. In addition, synthetic fertilizers may not support beneficial microbial populations to the same extent as natural fertilizers.

Special-purpose fertilizers are packaged for plants such as camellias, rhododendrons, and azaleas (Figure 1–43). Some of the compounds used in these fertilizers have an acid reaction that can be beneficial to acid-loving plants if the soil they are growing in is naturally neutral or alkaline; however, most soils in North Carolina are usually acidic so these special fertilizers are unnecessary.

Fertilizer spikes or pellets are fertilizers compressed into a form placed in the soil or pots (Figure1–44). They are convenient, but are expensive per unit of fertilizer and do not provide uniform distribution. Nutrients are often concentrated around the spikes or pellets.

Liquid fertilizer can be purchased as a dry powder or as a concentrated liquid (Figure 1–45). Liquid fertilizers are frequently used for houseplants or as a starter solution for transplants. They tend to be more expensive per unit of fertilizer because they are made from refined chemicals.

Foliar fertilizers are dry powders or concentrated liquids that are mixed with water and sprayed on plants (Figure 1–46). Foliar feeding is used when insufficient fertilizer was applied before planting, when a quick growth response is wanted, when micronutrients are locked in the soil, or when the soil is too cold for the plant to use fertilizer in the soil. Foliar-applied nutrients are absorbed and used by the plant quite rapidly. They are expensive per unit of nutrient and only give short-term fertilization (completely absorbed within one to two days). Relying totally on foliar fertilization can be time consuming because the fertilizer must be applied regularly. Improper foliar application of fertilizers can also lead to plant tissue burn.

Learn more about fertilizer usage and nutrient concentrations in the North Carolina Agricultural Chemicals Manual, Chapter IV – Fertilizer Use.

Fertilizer Terms

Fertilizer analysis: The minimum amount of each element in a fertilizer as stated on the label, such as 16-4-8.

Fertilizer ratio: The relative proportion of N, P2O5, and K2O. The ratios of 16-4-8 and 8-2-4 are both 4:1:2, which means 4 parts nitrogen to 1 part phosphorus to 2 parts potassium.

Balanced fertilizer: A fertilizer containing equal parts of each major element, such as 10-10-10.

Complete fertilizer: A fertilizer containing nitrogen, phosphorus, and potassium. Examples of commonly used fertilizers are 10-10-10, 16-4-8, and 12-4-8.

Incomplete fertilizer: A fertilizer missing one or two of the macronutrients, such as 0-20-0.

Weed and feed fertilizers: A combination of fertilizer and herbicide. They are often used on lawns to prevent certain weeds from germinating, or to kill existing broadleaf weeds.

High analysis: A fertilizer containing 30% or more active nutrients, such as ammonium nitrate 33-0-0. The cost per bag is usually more, but the cost per pound of nutrient is less, lowering the cost for fertilizing a given area.

Incomplete fertilizers can be used separately or combined to supply the needed nutrients, often at a reduced cost compared to using a complete fertilizer. For example, gardeners who have a soil with sufficient P and K can save money by applying a nitrogen-only fertilizer, such as ammonium nitrate (34-0-0). If a soil test indicates N and K are needed, but not P, use an appropriate amount of ammonium nitrate and muriate of potash (0-0-60), a naturally occurring material composed almost entirely of potassium, processed to remove impurities and concentrate the product. If a soil needs only P, use triple super phosphate (0-46-0), or for an organic nutrient source apply bone meal (approximately 3-15-0; note that this will add some N) or compost.

Regardless of the fertilizers used, be aware that excess fertilizer can damage plants and move into our stormwater systems, which can cause serious environmental problems.

Plant Nutrients and the Environment

Fertilizer misuse causes environmental and water quality issues. Nitrogen fertilizers, for instance, break down into ammonium and nitrate. The nitrate form of N, while essential for plant growth, is highly mobile and can move through the soil after rainfall or irrigation and contaminate drinking water supplies. Phosphorus holds tightly to soil particles and does not leach through the soil, but affects water quality through runoff and soil erosion. Excess nitrogen and phosphorus are associated with algal blooms (heavy growth of aquatic plants) and limited oxygen, and cause fish kills in lakes, bays, and nonflowing water bodies.

There are several ways to reduce fertilizers’ impacts on water quality:

  • Apply only materials that are recommended based on results of a soil test. If possible, use slow-release fertilizers and incorporate into the soil. Avoid applying excess nitrogen and phosphorus fertilizer.
  • Calibrate fertilizer spreaders properly and clean spreaders over the lawn area instead of a hard surface.
  • Keep the amount of hard surfaces in a landscape to a minimum. When installing a new sidewalk or patio, consider using gravel, porous concrete, stepping-stones, wood decking, or bricks on a sand base (Figure 1–47).
  • Avoid applying fertilizer to hard surfaces, such as sidewalks, patios, driveways, and streets. Sweep up material that falls on hard surfaces.
  • Maximize water absorption by aerating lawns and incorporating organic matter in planting beds and gardens.
  • Prevent runoff by turning off irrigation when the soil is no longer absorbing water.
  • Avoid applying fertilizer in natural drainage areas or ditches.
  • Minimize soil erosion by using ground covers, windbreaks, terraces, and mulches.
  • Mulch under trees and shrubs to reduce impact of falling water.
  • Maintain a lawn border around planting areas and plant a grass strip between rows in fruit and vegetable gardens.
  • Plant cover crops on bare soil, such as barren vegetable gardens.
  • Use a rain barrel under drains to collect runoff and direct excess runoff from roofs onto grassy areas (Figure 1–48).

When to Apply Fertilizer

Soil type affects the frequency of fertilizer application. Sandy soils require more frequent applications of smaller amounts of nitrogen and potash than do clay soils because these nutrients leach more readily in sandy soils. Other factors that affect application frequency include the plant to be grown, the amount of plant growth desired, the amount of water, and the type and release rate of fertilizer applied.

The best time to apply fertilizer and the most effective method of applying it depend on the type of plants being grown. Leafy vegetables require more nitrogen than root crops. Corn is a heavy nitrogen feeder and may require several small nitrogen applications when actively growing. Most established woody plants perform well without fertilization, or with just one application per year. Young plants may benefit from several light applications of fertilizer per year.

Fertilizer is needed when plants are actively growing, never when they are dormant. Nitrogen application will have its greatest effect three to four weeks after application. Excess or improperly timed nitrogen can delay flowering and fruiting or promote tender new growth vulnerable to frost or freeze damage.

Research has shown it is best to broadcast or incorporate fertilizer uniformly over an area rather than concentrating fertilizer in holes or bands in the soil. The most effective method of fertilizing a large area is with a fertilizer spreader; for home gardens, hand fertilization works fine. For new plantings, incorporate fertilizer into the soil and mix it thoroughly. For established plantings, surface application is appropriate.

When fertilizing from overhead, make certain plant foliage is dry and use a broom to brush fertilizer off the foliage, or water thoroughly after applying fertilizer to remove it from plant leaves to prevent burn spots. It is not necessary to remove mulch when fertilizing; irrigation or rainfall will carry fertilizer to the roots. Fertilization should be reduced or delayed during dry weather because the salts in the fertilizer can burn roots if there is inadequate moisture.

Calibrating a Spreader

Fertilizers are more effective if they are applied at the proper rate and with uniform coverage. To accomplish this, calibrate the spreader, which requires a little labor and math.

The two types of spreaders used to apply fertilizer and lime are drop spreaders (Figure 1–49) and rotary spreaders (Figure 1–50). The amount of fertilizer that is spread depends on the opening setting, the type of fertilizer, and the speed at which the spreader is pushed. The drop spreader has a series of holes at the base that can be adjusted to apply different amounts of material. With the rotary spreader, the fertilizer falls into a rotating plate and is spread by the centrifugal force of the plate spinning. Instructions for calibrating a spreader should be available on the Internet at the home page for the spreader manufacturer.

The Biology of Soil

There is more life below the soil surface than there is above. Soil life consists of burrowing animals, such as moles and earthworms, insects, and other soil creatures that are difficult or impossible to see without a microscope, such as mites, springtails, nematodes, viruses, algae, bacteria, yeast, actinomycetes, fungi, and protozoa. There are about 50 billion microbes in 1 tablespoon of soil. In a typical soil, each gram (what a standard paperclip weighs) likely contains these organisms, listed from largest to smallest:

 

  • Nematodes—10 to 5,000
  • Algae—1,000 to 500,000
  • Protozoa—1,000 to 500,000
  • Fungi—5,000 to 1,000,000
  • Actinomycetes—1,000,000 to 20,000,000
  • Bacteria—3,000,000 to 500,000,000

Soil-dwellers move through the soil, creating channels that improve aeration and drainage. Nematodes and protozoa swim in the film of water around soil particles and feed on bacteria. Mites eat fungi, and fungi decompose soil organic matter. The microorganisms’ primary role is to break down organic matter to obtain energy. Microorganisms help release essential nutrients and carbon dioxide and perform key roles in nitrogen fixation, the nitrogen and phosphorus cycles, denitrification, immobilization, and mineralization. Microbes must have a constant supply of organic matter, or their numbers will decline. Conditions that favor soil life also promote plant growth.

 

Unfavorable soil conditions, such as high temperatures, compaction, or oversaturation can injure beneficial soil life. This can lead to a proliferation of disease-causing fungi, bacteria, or viruses. To read more about common soil diseases see chapter 5,“Diseases and Disorders.” Plants that are stressed by disease are often more susceptible to insect damage. More information on insects can be found in chapter 4, “Insects.” To learn more about managing insects and diseases, please see chapter 8, “IPM .”

 

To promote soil organisms, incorporate organic matter, till as little as possible, minimize soil compaction, maintain favorable soil pH and fertility, and use organic mulch on the soil surface.

Further Reading

 

Brady, Nyle C., and Ray R. Weil. The Nature and Properties of Soils. 14th ed. Upper Saddle River, New Jersey: Prentice Hall, Inc, 2007. Print.

 

Buol, S. W., et al. Soil Genesis and Classification. 6th ed. Hoboken, New Jersey: John Wiley & Sons Inc., 2011. Print.

 

Dunne, Niall, ed. Healthy Soils for Sustainable Gardens. Brooklyn, New York: Brooklyn Botanic Garden, 2009. Print.

 

Maynard, Donald N., and George J. Hochmuth. Knott’s Handbook for Vegetable Growers. 5th ed. Hoboken, New Jersey: John Wiley & Sons, Inc., 2007. Print.

 

Soil Fertility Manual. 5th ed. Peachtree Corners, Georgia: International Plant Nutrition Institute, 2003. Print.

 

Table 1–4. Essential Nutrients for Plant Growth

MACRONUTRIENTS
NutrientWhy Nutrient is NeededDeficiency SymptomsExcess SymptomsComments
Nitrogen (N)• Responsible for rapid foliage growth and green color
• Easily leaches from soil
• Mobile in plant, moving to new growth
• Reduced growth (Figure 1–30)
• Light-green to yellow foliage (chlorosis)
• Reds and purples may intensify with some plants
• Reduced lateral breaks
• Symptoms appear first on older growth
• Succulent growth; leaves are dark green, thick, and brittle
• Poor fruit set
• Excess ammonia can induce calcium deficiency
• High N under low light can cause leaf curl
• Uptake inhibited by high P levels
Phosphorus (P)• Promotes root formation and growth
• Affects quality of seed, fruit, and flower production
• Increased disease resistance
• Does not leach from soil readily
• Mobile in plant, moving to new growth.
• Reduced growth
• Leaves dark-green; purple or red color in older leaves, especially on the underside of the leaf along the veins (Figure 1–31)
• Leaf shape may be distorted
• Thin stems
• Limited root growth
Shows up as micronutrient deficiency of Zn, Fe, or Co• Rapidly fixed on soil particles
• When applied under acid conditions, fixed with Fe, Mn, and Al
• High P interferes with micronutrient and N absorption
• Used in relatively small amounts when compared to N and K
• Availability is lowest in cold soils
Potassium (K)• Helps plants overcome drought stress
• Improves winter hardiness
• Increases disease resistance
• Improves the rigidity of stalks
• Leaches from soil
• Mobile in plant
• Reduced growth
• Shortened internodes
• Margins of older leaves become chlorotic and burned
• Necrotic (dead) spots on older leaves (Figure 1–32)
• Reduction of lateral breaks and tendency to wilt readily
• Poorly developed root systems
• Weak stalks
Causes N deficiency and may affect the uptake of other nutrients• High N/low K favors vegetative growth
• Low N/high K promotes reproductive growth (flower, fruit)
• Calcium excess impedes uptake of K
Magnesium (Mg)• Leaches from sandy soil
• Mobile in plant
• Reduction in growth
• Yellowish, bronze, or reddish color of older leaves, while veins remain green (Figure 1–33)
• Leaf margins may curl downward or upward with a puckering effect
• Interferes with Ca uptake
• Small necrotic spots in older leaves
• Smaller veins in older leaves may turn brown
• In advanced stage, young leaves may be spotted
• Mg is commonly deficient in foliage plants because it is leached and not replaced
• Epsom salts at a rate of 1 teaspoon per gallon may be used two times a year
• Mg can be absorbed by leaves if sprayed in a weak solution
• Dolomitic limestone can be applied in outdoor situations to rectify a deficiency
Calcium (Ca)• Moderately leachable
• Limited mobility in plant
• Essential for growth of shoot and root tips
• Inhibition of bud growth
• Roots can turn black and rot
• Young leaves are scalloped and abnormally green
• Leaf tips may stick together
• Cupping of maturing leaves
• Blossom end rot of many fruits (Figure 1–34)
• Pits on root vegetables; stem structure is weak
• Premature shedding of fruit and buds
• Interferes with Mg absorption
• High Ca usually causes high pH
Ca is rarely deficient if the correct pH is maintained
Sulfur (S)• Leachable
• Not mobile
• Contributes to odor and taste of some vegetables
• Rarely deficient
• General yellowing of the young leaves, then the entire plant (Figure 1–35)
• Veins lighter in color than adjoining interveinal area
• Roots and stems are small, hard, and woody
Sulfur excess is usually in the form of air pollutionSulfur excess is difficult to control, but rarely a problem

MICRONUTRIENTS

NutrientWhy Nutrient is NeededDeficiency SymptomsExcess SymptomsComments
Iron (Fe)• Accumulates in the oldest leaves and is relatively immobile
• Necessary for the maintenance of chlorophyll
• Interveinal chlorosis primarily on young tissue, which may become white (Figure 1–36)
• Fe deficiency may occur even if Fe is in the soil when: soil is high in Ca; soil is poorly drained; soil is oxygen deficient; nematodes attack roots; or soil is high in Mn, pH, or P
• Fe should be added in the chelate form; the type of chelate needed depends upon the soil pH
• Foliar fertilization will temporarily correct the deficiency
• May be deficient in centipede grass where pH and P are high
Rare except on flooded soils 
Boron (B)• Important in enabling photosynthetic transfer
• Very immobile in plants
• Failure to set seed
• Internal breakdown of fruit or vegetable
• Death of apical buds, giving rise to witches’ broom
• Failure of root tip to elongate normally
• Young leaves become thick, leathery, and chlorotic (Figure 1–37)
• Rust-colored cracks and corking on young stems, petioles, and flower stalks (such as heart rot of beets, stern crack of celery)
• Breakdown occurs at the base of the youngest shoots

• Tips and edges of leaves exhibit necrotic spots coalescing into a marginal scorch (similar to high-soluble salts) (Figure 1–38)
• Oldest leaves are affected first • Can occur in low pH soils • Plants are easily damaged by excess application •Looks like Mg deficiency,green veins on a yellow leaf.

 
Zinc (Zn)Needed for enzyme activity• Young leaves are very small, sometimes missing leaf blades
• Short internodes
• Distorted or puckered leaf margins
• Interveinal chlorosis (Figure 1–39)
• Severe stunting, reddening
• Poor germination
• Older leaves wilt
• Entire leaf is affected by chlorosis; edges and main vein often retain more color
• Can be caused by galvanized metal.
 
Copper (Cu)Needed for enzyme activity• New growth small, misshapen, wilted (Figure 1–40)
• In some species, young leaves may show interveinal chlorosis while tips of older leaves remain green
• Can occur at low pH
• Shows up as Fe deficiency
 
Manganese (Mn)Needed for enzyme activity• Interveinal chlorosis with smallest leaves remaining green, producing a checkered effect (Figure 1–41)
• Grey or tan spots usually develop in chlorotic areas
• Dead spots may drop out of the leaf
• Poor bloom size and color
• Induced by excessively high pH
• Reduction in growth, brown spotting on leaves
• Shows up as Fe deficiency
• Found under strongly acidic conditions
 
Molybdenum (Mo)Needed for enzyme activity• Interveinal chlorosis on older or midstem leaves (Figure 1–42)
• Twisted leaves whiptail
• Marginal scorching and rolling or cupping of leaves
• Nitrogen deficiency symptoms may develop
• Intense yellow or purple color in leaves
• Rarely observed
 
Chlorine (Cl)Needed for enzyme activity• Wilted leaves which become bronze, then chlorotic, then die
• Club roots
• Salt injury
• Leaf burn
• May increase succulence
 
Cobalt (Co)• Needed by plants recently established
• Essential for nitrogen fixation
Little is known about its deficiency symptomsLittle is known about its toxicity symptoms 
Nickel (Ni)• Needed by plants recently established
• Essential for seed development
Little is known about its deficiency symptomsLittle is known about its toxicity symptoms 

 

Related Images:

The Role of Phosphorus (P)

Phphosphorus_deficiency1osphorus is a vital component of adenosine triphosphate (ATP), the ‘energy unit’ of plants. ATP forms during photosynthesis, has P in its structure, and processes from the beginning of seedling growth through to the formation of grain and maturity.

Periodic Table of Crop Nutrients and Deficiencies

Periodic Table of Crop Nutrients

17 nutrients are essential for plant health. Optimal yields can only be produced when all these nutrients are in proper supply. According to the Law of Minimum, if one or more nutrients are lacking in the soil, crop yields will be reduced, even though an adequate amount of other elements is available.

Plumeria Nutrient Deficiencies

Not all plumeria problems are caused by insects or diseases. Sometimes an unhealthy plumeria is suffering from a nutrient deficiency or even too much of any one nutrient. Plumeria nutrient deficiencies often manifest as foliage discoloration or distortion. The following chart outlines some possible problems. Unfortunately many problems have similar symptoms and sometimes it is a combination of problems.

Be sure you eliminate the obvious before you kill your plumeria with kindness.

  • Check first for signs of insects or disease.
  • Foliage discoloration and stunted plants can easily be caused by soil that is too wet and drains poorly or soil that is too compacted for good root growth.
  • Exposure to cold or heat will slow plant growth and effect flowering.
  • Too much fertilizer can result in salt injury. Your plants may look scorched or they may wilt, even when the soil is wet.

Plumeria require a mix of nutrients to remain healthy. Nutrients that are needed in relatively large amounts are called the macronutrients. Plant macronutrients include: (N) nitrogen, (P) potassium, (K) phosphorus, calcium, sulfur and magnesium.

There are a handful of additional nutrients that are required for plant growth, but in much smaller quantities. These micronutrients include: boron, copper, iron, manganese, molybdenum and zinc.

All of these nutrients are taken in through the roots. Water transfers the nutrients from the soil to the Plumeria roots. So one requirement of sufficient Plumeria nutrition is water. A second requirement is the appropriate soil pH for the Plumeria being grown. Each Plumeria prefers a specific pH range to be able to access the nutrients in the soil. Some Plumeria are fussier than others, but if the soil pH is too acidic or alkaline, the Plumeria will not be able to take in nutrients no matter how rich your soil may be.

Primary Macronutrients

nutrient-deficiency-chart

Nitrogen (N) 

Nitrogen (N) is essential for plant growth and is part of every living cell. It plays many roles in plants and is necessary for chlorophyll synthesis. Plants take up most of their N as the ammonium (NH4+) or nitrate (NO3) ion. Some direct absorption of urea can occur through the leaves, and small amounts of N are obtained from materials such as water-soluble amino acids.

  • Symptoms: Lack of N and chlorophyll means the plant will not utilize sunlight as an energy source to carry on essential functions such as nutrient uptake. Older leaves, generally at the bottom of the plant, will yellow. Remaining foliage is often light green. Stems may also yellow and may become spindly. Growth slows. 
  • Sources: Any compound containing the words: ‘nitrate’, ‘ammonium’ or ‘urea’. Also manure.
  • Notes:
    • Many forms of nitrogen are water soluble and wash away.
    • Nitrogen is a component of vitamins, amino acids and energy systems within the plant, which form its proteins. Thus, N is directly responsible for increasing protein content in plants.
    • Nitrogen is necessary for chlorophyll synthesis and, as a part of chlorophyll molecules, is involved in photosynthesis.
    • Nitrate is very mobile in the soil and moves with soil water to root surfaces for plant absorption.

Phosphorus (P)

One of three primary nutrients, phosphorus (P) is essential for plant growth, and a plant must access it to complete its normal production cycle. Plants absorb P from the soil as primary and secondary orthophosphates (H2PO4 and HPO42-).

  • Symptoms: Small leaves that may take on a reddish-purple tint. Leaf tips can look burnt and older leaves become almost black. Reduced fruit or seed production.
  • Sources: Compounds containing the words ‘phosphate’ or ‘bone’. Also green sand.
  • Notes:
    • Very dependent on pH range.
    • The highest levels of P in young plants are found in tissue at the growing point. As crops mature, most P moves into the seeds, fruit, or both.
    • Under P deficiency, some crops, such as corn, tend to show abnormal discoloration.
    • Phosphorus is noted especially for its role in capturing and converting the sun’s energy into useful plant compounds.
    • Phosphorus promotes root development and early seedling growth.
    • Research associates specific growth factors with P: stimulated root development, increased stalk and stem strength, and improved flower formation and seed production.

Potassium (K)

Potassium (K) is one of the essential nutrients and is taken up in significant amounts by crops. Potassium is vital to photosynthesis, protein synthesis and many other functions in plants. It’s classified as a macronutrient, as are nitrogen (N) and phosphorus (P). Plants take up K in its ionic form (K+).

  • Symptoms: Older leaves may look scorched around the edges and/or wilted. Interveinal chlorosis (yellowing between the leaf veins) develops.
  • Sources: Compounds containing the words ‘potassium’ or ‘potash’.
  • Notes:
    • Potassium enhances many enzyme actions aiding in photosynthesis and food formation. It builds cellulose and helps translocate sugars and starches. Potassium is vital to producing grains rich in starch.
    • Potassium maintains turgor and reduces water loss and wilting.
    • Potassium is known as the “quality nutrient” because of its important effects on factors such as size, shape, color, taste, shelf life, fiber and other quality-related measurements.
    • In many high-yielding crops, the K content in the plant is comparable to the nitrogen (N) content.
    • Potassium is absorbed by plants in the ionic form, indicated as K+.
    • Plants deficient in K are less resistant to drought, extreme temperatures and other stressors. Plants lacking K are also more susceptible to pests, diseases and nematode attacks.
    • Ample K can increase root growth and improves drought tolerance.

Secondary Macronutrients

Magnesium (Mg)

Hidden in the heart of each chlorophyll molecule is an atom of magnesium (Mg), making the nutrient actively involved in photosynthesis. Magnesium also aids in phosphate metabolism, plant respiration and the activation of many enzyme systems.

  • Symptoms: Slow growth and leaves turn pale yellow, sometimes just on the outer edges. New growth may be yellow with dark spots.
  • Sources: Compounds containing the word ‘magnesium’, such as Epson Salts.
  • Notes:
    • Magnesium is mobile within the plant and moves easily from older to younger tissues.
    • Plants require Mg to capture the sun’s energy for growth and production through photosynthesis.
    • When Mg deficiencies occur, the lower (older) leaves are affected first.
    • The most common source of Mg is dolomitic limestone, which provides both calcium and Mg, while neutralizing soil acidity.
    • Magnesium acts as a phosphorus carrier in plants, and is required for better root formation and thus for better nutrient and water efficiency in plants.

Calcium (Ca)

Calcium (Ca) is found all around us, and the very existence of plants and animals depends on it. Plants take up Ca as the Ca2+ cation. Once inside the plant, Ca functions in several essential ways.

  • Symptoms: New leaves are distorted or hook shaped. The growing tip may die. Contributes to blossom end rot in tomatoes, tip burn of cabbage and brown/black heart of escarole & celery.
  • Sources: Any compound containing the word ‘calcium’. Also gypsum.
  • Notes:
    • Not often a deficiency problem and too much will inhibit other nutrients.
    • Calcium deficiencies occur most often in acidic, sandy soils from which Ca leaches via rain or irrigation water.
    • Calcium helps balance organic acids within the plant as well as activates several plant enzyme systems.
    • Calcium helps form the compounds that make up part of cell walls, which in turn, strengthen the plant structure.
    • Calcium builds yields by indirectly improving root growth conditions and stimulating microbial activity, molybdenum (Mo) availability and uptake of other nutrients.
    • Calcium helps enable nitrogen (N)-fixing bacteria that form nodules on the roots of leguminous plants to capture atmospheric N gas and convert it into a form plants can use.
    • Calcium stimulates root and leaf development, and affects uptake and activity of other nutrients.

Sulfur (S)

Sulfur (S) is a part of every living cell and is important in the formation of proteins. Unlike the other secondary nutrients like calcium and magnesium (which plants take up as cations), S is absorbed primarily as the SO42- anion. It can also enter plant leaves from the air as dioxide (SO2) gas.

  • Symptoms: New growth turns pale yellow, older growth stays green. Stunts growth.
  • Sources: Compounds containing the word ‘sulfate’.
  • Notes:
    • More prevalent in dry weather.
    • Sulfur is present in several organic compounds that give the characteristic odors to garlic, mustard and onion.
    • Sulfur appears in every living cell and is required for synthesis of certain amino acids (cysteine and methionine) and proteins.
    • Sulfur is also important in photosynthesis and for winter crop hardiness.
    • Although S isn’t a constituent of cholrophyll, it’s still vital in chlorophyll formation.
    • Sulfur aids in seed production.
    • Leguminous plants need S for efficient nitrogen fixation.

Micronutrients

Boron (B)

Boron (B) is a micronutrient that is essential for cell wall formation and rapid growing points within the plant, such as reproductive structures. Interestingly, while higher plants require B, animals, fungi and microorganisms do not need this nutrient.

  • Symptoms: Poor stem and root growth. Terminal (end) buds may die. Witches brooms sometimes form.
  • Sources: Compounds containing the words ‘borax’ or ‘borate’.
  • Notes:
    • Boron improves seed set under stressful conditions.
    • Although required in small amounts, boron is a component of all cell walls in the plant.
    • Boron deficiencies are more pronounced during drought periods, when root activity is restricted.
    • The line between deficiency and toxicity is narrower than other essential nutrients. Farmers should apply at proper rate and with proper placement.
    • Plumeria most effectively uses boron when it’s applied through broadcast soil applications.

Chlorine (Cl)

Plants take up chlorine (Cl) as the chloride (Cl) anion. It’s active in energy reactions in the plant. Most Cl in soils comes from salt trapped in parent materials, marine aerosols and volcanic emissions. Classified as a micronutrient, Cl is required by all plants in small quantities.

  • Symptoms:
  • Sources:
  • Notes:
    • Stomata regulate the release of moisture from plants so they can minimize water loss during stressful dry periods. Chloride is key in stomatal regulation.
    • Chloride is involved in the chemical breakdown of water in the presence of sunlight and activates several enzyme systems.
    • Chloride plays an important role in plants as they acclimate to changing water availability (or make osmotic adjustments).
    • Chloride supports the transport of nutrients such as calcium, magnesium and potassium within a plant.

Copper (Cu)

Copper (Cu) activates enzymes and catalyzes reactions in several plant-growth processes. Vitamin A production is closely linked to the presence of Cu as well, and it helps ensure successful protein synthesis. Classified as a micronutrient, only a small amount of this essential nutrient is needed for plant survival.

  • Symptoms: Stunted growth. Leaves can become limp, curl, or drop. Seed stalks also become limp and bend over.
  • Sources: Compounds containing the words ‘copper’, ‘cupric’ or ‘cuprous’.
  • Notes:
    • Copper is the most immobile of the micronutrients.
    • Many vegetable crops show Cu hunger, with leaves that lose turgor and develop a bluish-green shade before becoming chlorotic and curling.
    • Copper is necessary to chlorophyll formation in plants and catalyzes several other plant reactions.
    • Other metals in the soil, such as iron, manganese and aluminum, affect the availability of Cu for plant growth.
    • Organic soils are the most vulnerable to Cu deficiency; heavy, clay-type soils are least vulnerable.

Manganese (Mn)

Manganese (Mn) functions primarily as part of enzyme systems in plants. It activates several important metabolic reactions and plays a direct role in photosynthesis. Manganese accelerates germination and maturity while increasing the availability of phosphorus (P) and calcium (Ca).

  • Symptoms: Growth slows. Younger leaves turn pale yellow, often starting between veins. May develop dark or dead spots. Leaves, shoots and fruit diminished in size. Failure to bloom.
  • Sources: Compounds containing the words ‘manganese’ or ‘manganous’
  • Notes:
    • Manganese plays a vital role in photosynthesis by aiding in chlorophyll synthesis.
    • Soybeans and wheat in particular require more Mn than many crops.
    • Manganese is very immobile in plants, so deficiency symptoms appear first on younger leaves, with yellowing between the veins. Sometimes a series of brownish-black specks appear.
    • Although Mn deficiencies are often associated with high soil pH, they may result from an imbalance with other nutrients such as calcium (Ca), magnesium (Mg), and Iron (Fe).
    • Manganese deficiencies are most common in high organic matter soils and in those soils with naturally low Mn content and neutral to alkaline pH.

Iron (Fe)

Iron (Fe) is essential for crop growth and food production. Plants take up Fe as the ferrous (Fe2+) cation. Iron is a component of many enzymes associated with energy transfer, nitrogen reduction and fixation, and lignin formation.

  • Symptoms: Plants deficient in Fe will often display a pale green leaf color (chlorosis), with sharp distinction between green veins and yellow interveinal tissues. Iron deficiencies may be caused by an imbalance with other metals such as copper (Cu), manganese (Mn) and molybdenum (Mo).
  • Sources:
  • Notes:
    • Iron deficiencies may be caused by an imbalance with other metals such as copper (Cu), manganese (Mn) and molybdenum (Mo).
    • Plants deficient in Fe will often display a pale green leaf color (chlorosis), with sharp distinction between green veins and yellow interveinal tissues.
    • Most Fe fertilizer sources work best applied as foliar sprays.
    • Iron is a catalyst to chlorophyll formation.
    • Iron acts as an oxygen carrier in the nodules of legume roots.

Molybdenum (Mo)

Molybdenum (Mo) is a trace element found in the soil and is required for the synthesis and activity of the enzyme nitrate reductase. Molybdenum is vital for the process of symbiotic nitrogen (N) fixation by Rhizobia bacteria in legume root modules. Considering Mo’s importance in optimizing plant growth, it’s fortunate that Mo deficiencies are relatively rare in most agricultural cropping areas.

  • Symptoms: Older leaves yellow, remaining foliage turns light green. Leaves can become narrow and distorted.
  • Sources: Compounds containing the words ‘molybdate’ or ‘molybdic’.
  • Notes:
    • Sometimes confused with nitrogen deficiency.
    • Molybdenum-deficiency symptoms show up as a general yellowing and stunting of the plant. A Mo deficiency can also cause marginal scorching and cupping or rolling of leaves.
    • Several materials supply Mo and can be mixed with nitrogen (N), phosphorus (P) and potassium (K) fertilizers applied as foliar sprays or used as a seed treatment. Seed treatment is the most common way of correcting Mo deficiency because of the very small amounts of the nutrient required.
    • Plants take up Mo as the MoO42- anion.
    • Molybdenum becomes more available as soil pH goes up, the opposite of most other micronutrients
    • Excessive Mo is toxic, especially to grazing animals.

Zinc (Zn)

Zinc (Zn) is taken up by plants as the divalent Zn2+ cation. It was one of the first micronutrients recognized as essential for plants and the one most commonly limiting yields. Although Zn is required in small amounts, high yields are impossible without it.

  • Symptoms: Yellowing between veins of new growth. Terminal (end) leaves may form a rosette.
  • Sources: Compounds containing the word ‘zinc’.
  • Notes:
    • Can become limited in higher pH.
    • Protein synthesis and growth regulation require Zn. Reduced hormone production due to a Zn-deficient plant will cause the shortening of internodes and stunted leaf growth.
    • Zinc is much less mobile within the plant, so deficiency symptoms first appear on the younger leaves.
    • Zinc aids synthesis of plant-growth substances and enzyme systems, and is essential for promoting certain metabolic reactions, which are particularly critical in the early growth stages.
    • As soil pH increases, zinc availability decreases.

Nickel (Ni) was added to the list of essential plant nutrients late in the 20th century. Plants absorb Ni as the divalent cation Ni2+. It is required in very small amounts, with the critical level appearing to be about 0.1 parts per million.

  • Notes:
    • No Ni deficienceies have been observed under crop-growing conditions, but in crop research settings, ag scientists have reproduced deficiency symptoms such as chlorosis of young leaves and dead meristematic tissue.
    • Nickel deficiency has been observed in some nursery plants and tree crops. Affected trees develop mouse-ear, a condition marked by small, curled leaves and stunted growth.
    • Nickel is a component of the urease enzyme and is, therefore, necessary for the conversion of urea to ammonia (NH3) in plant tissue, making it important in plant nitrogen (N) metabolism.

Non-fertilizer Elements

Hydrogen (H)

Hydrogen (H), derived almost entirely from water, is one of the 17 essential nutrients necessary for plant growth. Hydrogen, along with carbon and oxygen, are the three primary elements plants use in the largest amounts, and they perform as the building blocks for plant growth.

  • Notes:
    • Nearly all organic compounds also contain H atoms, which explains why plants need the H they get from water molecules through photosynthesis.
    • Hydrogen ions are vital in both aiding proton gradients to help drive the electron transport chain in photosynthesis, and for plant respiration.
    • Hydrogen is necessary for building sugars and other molecules to produce glucose for plant energy.
    • Known as a structural element, H is present in both the atmosphere and the growing environment.
    • Hydrogen is rarely a limiting nutrient.
    • Hydrogen is an element and can be a compound as well. As an element, H is the lightest, with one proton, one electron and usually no neutrons. Compound H forms when two H atoms share an electron pair, creating a covalent bond, which takes the form of a gas.

Carbon (C)

Carbon (C) is responsible for all life on earth. Carbon dioxide (CO2) released into the atmosphere is recycled endlessly as part of the carbon cycle. Plants take CO2 from the air and use the C for energy, helping to build essential biological compounds such as carbohydrates and proteins.

  • Notes:
    • Carbon is the primary energy source and building block for plant tissues.
    • Converted through photosynthesis into simple sugars, C helps plants build starches, carbohydrates, cellulose, lignin and protein.
    • Crop residues, green manures and animal wastes can be significant sources of organic C in the soil.
    • Almost half of the plant’s dry matter is comprised of C.

Oxygen (O)

Oxygen (O) is responsible for cellular respiration in plants. Plants acquire O by breaking down carbon dioxide (CO2) during photosynthesis and end up releasing the majority of it as an unnecessary byproduct, saving a small portion for future energy.

  • Notes:
    • All Oxygen available to life on Earth comes from plants.
    • Most of the Oxygen plants take in is expelled as a byproduct. Only a very small amount is actually used by the plant for respiration.
    • Plants don’t absorb Oxygen from the air, but instead acquire it during the breakdown of carbon dioxide (CO2) as part of photosynthesis.
    • Oxygen interacts with nitrogen (N) in a process called denitrification, and it affects other elements’ oxidation states as well.
    • Only the leaves and stems of a plant acquire Oxygen through photosynthesis. The roots of a plant are forced to take in Oxygen from the environment through air spaces in the soil.

Related Images:

The Role of Nitrogen (N)

Nitrogen (N) is essential for plant growth and is part of every living cell. It plays many roles in plants and is necessary for chlorophyll synthesis. Plants take up most of their N as the ammonium (NH4+) or nitrate (No3-) ion. Some direct absorption of urea can occur through the leaves, and small amounts of N are obtained from materials such as water-soluble amino acids.

Phosphorus deficiency guide

 

phosphorusPhosphorus (K) deficiency guide

Phosphorus plays an important role for all living organisms and is an essential nutrient element for plants and animals. It has a key position in the combustion processes of the cell, and in the total energy transfer of the plant. It is also a “building block” of the cell walls, the DNA, and all sorts of proteins and enzymes.
 

For young plants, the presence of phosphate is indispensable; about 3/4 of the phosphorus consumed during a plant’s life cycle is absorbed in the first quarter of its life. The largest concentrations of phosphorus are found in the developing parts of the plant: the roots, the growth shoots and the vascular tissue.

 

About phosphorus in short

What is it and what does it do?
Phosphorus holds a key position in both cell processes and total energy transfer of the plant.
Also a “building block” of – among others – cell walls and DNA.
What can you see?
Small plant with purple/black necrotic leaf parts.
Leafs become malformed and shriveled.
What can you do?
Mix inorganic phosphate fertilizer THOROUGHLY through the potting mix or add extra liquid phosphate when growing in hydroponics.

Symptoms of a deficiency

Plants remain rather small with purple-black necrotic leaf parts, which later on become malformed and shriveled.

Development of a deficiency

  • At first, the plant becomes dark green – a different sort of dark green (blue/ green) as appears when there is a shortage of phosphorus.
  • The growth in height, and the development of the plant’s side shoots are inhibited.
  • After 2 to 3 weeks, dark purple-black necrotic spots appear on the old and medium-old leaves, making the leaves malformed.
  • The purple/black necroses expand to the leaf’s stem. The leaf turns, curls considerably and dies off.
  • The dead leaves are curled and shriveled, have a typical orange purple color, and fall off.
  • The plant flowers fully, but the yield will be minimal.

Reasons for a deficiency

Due to the low concentrations in which phosphate appears in nature, the affinity of plant cells for phosphorous allows easy absorption through the whole root. Therefore, shortages do not happen very often, except when:

  • The growing medium has a too high pH (higher than pH 7). In such cases the plant can not absorb phosphorus due to the fact that insoluble phosphorous compounds develop.
  • The ground is too acidic, or too rich in iron and zinc. This hinders the absorption of phosphate.
  • The potting mix has become fixated. Phosphate can not be absorbed any more.

Solutions to a deficiency

Always use inorganic phosphates as these are easy to absorb. Also always mix the phosphate fertilizer thoroughly through the potting mix.

  • When pH is too high, acidify the medium by using a thinned solution of phosphoric acid.
  • Choose products that have a guaranteed phosphate percentage on the packaging instead of alternative phosphate-containing products like guano or manure.

Related Images:

Calcium (Ca) deficiency guide

 

calciumCalcium deficiency guide


Calcium occurs throughout the entire plant. It is used for many processes in the plant, however, calcium is most important for the growth process. It has a regulating effect in the cells and contributes to the stability of the plant. Plants have two transportation systems at their disposal: the xylem vessels and the sieve vessels.
 

Most nutrients can be transported via both systems, however, for calcium this is not possible. Since calcium can be transported almost exclusively via the xylem vessels, it is an element that deposes of little mobility within the plant. It is, therefore, important that a sufficient amount of calcium is always available in the root environment, so that it will be continuously available for absorption by the plant.

 

About calcium in short

What is it and what does it do?
Calcium is important to the growth process.
Has a regulating effect in the cells and contributes to the stability of the plant.
What can you see?
Yellow/brown spots, surrounded by a sharp brown outlined edge.
What can you do?
Add calcium by applying a liquid lime fertilizer such as a calcium nitrate solution.

infocourier-calcium_text_4.jpg

 

Symptoms of a deficiency

The older, larger leaves just above the bottommost ones will show the first symptoms. Yellow/brown spots occur, which are often surrounded by a sharp brown outlined edge. In addition, the growth is curbed and in serious cases the tops are smaller than normal and do not close.

 

Development of a deficiency

The symptoms often appear quickly; within one or two weeks the first spots being visible on the older leaves. The spots usually start as small, light brown specks that increase in size over time.

  • After two weeks, the older leaves show ever increasing spots and the spots also often appear at the edge of the leaves, as with a potassium deficiency or with scorch symptoms. The spots have a sharp outline and do not originate exclusively at the edge of the leaves. A lag in development is often already noticeable within a week.
  • Sometimes the growing points will wrinkle up and around the fruits you will find thin, small leaves that are not spotted.
  • The older leaves die off slowly and yellowish cloudy spots may appear around the necrotic spots. The older the leaf is, the more serious the symptoms are.
  • The flowering is also hindered and slowed down. Fruits stay small.

infocourier-calcium_text_3.jpg

Reasons for a deficiency

  • Culture on calcium fixing potting mix.
  • An excessive amount of ammonium, potassium, magnesium and/ or sodium in the root environment. The absorption is curbed mostly by ammonium and least by sodium.
  • Problems with the evaporation caused by an excessively high EC value or by excessively high or low relative humidity.

Solutions to a deficiency

  • If the EC value of the substrate or the potting mix is too high, it can be easily rinsed out with pure and if necessary acidified water.
  • Additional calcium can be applied through the nutrient solution by means of liquid lime fertilizers such as a calcium nitrate solution. With an excessively acidic potting mix, lime milk can be used to increase the pH. Use the appropriate potting mix that is not too acidic. Acid potting mix often contains insufficient amounts of lime. Good potting mix and Coco substrates are already limed.

For your information: Be careful with fertilizers containing chloride.

Related Images:

Magnesium (Ca) deficiency guide

 

magnesium-elementMagnesium deficiency guide

Magnesium is an indispensable element for – amongst others – plants. In plants, it represents a building block for chlorophyll (leaf green), and therefore, it is essential for photosynthesis. At the same time, magnesium plays an important role in the energy transfer. Together with calcium, it is also a component of tap water, influencing water hardness. Inorganic magnesium fertilizers are produced using the same bases that are used to produce potassium fertilizers.

About magnesium in short

What is it and what does it do?
Magnesium is indispensable to plants as it is essential for photosynthesis.
Represents a building block for chlorophyll.
What can you see?
Rusty brown spots.
Cloudy, vague yellow spots between the veins.
What can you do?
Spray with a 2% solution of Epsom salts every 4-5 days during about a week.

infocourier-magnes_text_4.jpg

 Symptoms of a deficiency

When there is a shortage, the leaf green in the medium-old leaves under the flowering top will be broken up, and the magnesium will be transported into the young parts of the plant. This breakdown is visible as rusty brown spots and/ or vague, cloudy, yellow spots between the veins. A slight shortage of magnesium hardly affects flowering, although the development of the flowers make the deficiency symptoms worse.

Development of a deficiency

  • Signs of a deficiency first appear around the 4th-6th week. Small, rusty brown spots and/or cloudy yellow flecks appear in the middle-aged leaves (under the top of the plant).
  • The color of the young leaves and the fruit development are not affected.
  • The size and number of rust-brown spots on the leaves increase.
  • The symptoms spread out over the whole plant, which looks ill. When the shortage becomes acute, the younger leaves are also affected and the flower production will be reduced.

Reasons for a deficiency

The magnesium deficiency can occur because uptake is inhibited because of:

  • A very wet, cold and/or acidic root environment.
  • A high quantity of potassium, ammonia and/or calcium (for instance high concentrations of calcium carbonate in drinking water, or clay potting mixes rich in calcium) in comparison with the quantity of magnesium.
  • A limited root system and heavy plant demands.
  • A high EC in the growing medium, which hinders evaporation.

infocourier-magnes_text_3.jpgSolutions to resolve a deficiency

  • When a shortage is diagnosed, the best thing to do is to spray with a 2% solution of Epsom salts.
  • Fertilization via the roots: Inorganic: Epsom salts on hydroponics or Kieserite (magnesium sulphate mono hydrate). Organic: composted turkey or cow manure.

Recovery

Rectify the possible causes: In potting mixes, when the pH is too low (less than 5), use magnesium containing calcium fertilizers. In hydro, temporarily apply a nutrient solution with a higher pH (6.5). When the EC is too high, rinse and/or temporarily feed with drinking water only.

When growing indoors, keep the root temperature between 20 – 25 degrees Celsius. A little extra magnesium is not particularly harmful. When growing in potting mixes, excessive quantities of magnesium do not appear quickly. Too much magnesium inhibits the uptake of calcium, and the plant displays general symptoms of an excess of salts; stunted growth, and dark-colored vegetation.

Related Images:

Iron deficiency guide

Iron deficiency guide

Iron is a vital element for plant life. Iron has a number of important functions in the overall metabolism of the plant and is essential for the synthesis of chlorophyll. In general, iron is poorly absorbed by the plant. It can only be sufficiently taken up by the roots in certain forms and under proper conditions.

Potting mixes seldom contain too little iron, but it is possible that forms of iron that can be absorbed by the plant are lacking. The absorbency of iron is strongly dependent on the pH. Usually, there is sufficient iron present in absorbable form in acidic potting mixes.

About iron in short

What is it and what does it do?
Iron has a number of important functions in the plant’s overall metabolism and is essential for the synthesis of chlorophyll.
What can you see?
Strong yellowing of especially the young leaves and growth shoots between the veins.
What can you do?
The best thing is to spray the plants with a watery solution of EDDHA or EDTA chelates.

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Symptoms of a deficiency

Iron deficiency can occur during periods of heavy growth or high plant stress and is characterized by a strong yellowing of the young leaves and the growth shoots between the veins. This occurs chiefly because iron is not mobile in the plant. The young leaves can’t draw any iron from the older leaves. With a serious iron shortage, the older leaves and the smaller veins in the leaf can also turn yellow.

Development of a deficiency

  • Green/yellow chlorosis, from inside to the outside in the younger leaves and in the growth shoots. The veins remain mostly green.
  • Continued yellowing of the leaves to sometimes almost white. Also, large leaves turn yellow. This inhibits growth.
  • In serious cases the leaves show necrosis, and the plant’s growth and flowering are inhibited.

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Reasons for a deficiency

  • The pH in the root environment is too high (pH> 6,5).
  • The root environment contains a lot of zinc and/or manganese.
  • The concentration of iron is too low in the root environment.
  • The root temperature is low.
  • The root medium is too wet, causing the oxygen supply in the roots to stagnate.
  • The root system functions inefficiently due to damaged, infected or dead roots.
  • There is too much light on the nutrition tank; light promotes the growth of algae. Algae also use up the iron and break down iron chelates.

Solutions for a deficiency

  • Lower the pH.
  • Iron chelates can be added to the substrate.
  • Drainage can be improved, or the ground temperature can be increased.
  • A leaf nutrient with iron chelates can possibly be applied. If a good fertilizer is used with hydroponic growing, an iron deficiency is almost out of the question.
  • The best thing you can do is to spray the plants with a watery solution of EDDHA (max. 0.4 grams per gallon) or EDTA chelates (max. 2 grams per gallon).

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