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How to understand your tissue analysis report element by element

Total nitrogen

Nitrogen is a critical part of proteins in the plant. It is also an important part of chlorophyll and plays a key role in photosynthesis. Nitrogen-deficient plants generally have a pale green or yellow color. In grasses, yellowing usually starts at the tip of the leaf and goes down to the middle of the leaf. Because nitrogen is mobile in the plant, the oldest leaves will show symptoms first. The total N content of a plant includes all forms of nitrogen in the plant tissue. Total N content represents the nitrogen status of a crop up to that point in the growing season, but does not predict the crop's nitrogen status in the future.


Phosphorus is important for root growth, seed production and crop maturity along with many other functions. Symptoms of phosphorus-deficient plants include stunted growth, delayed maturity, and reduced seed production. In young plants, phosphorus deficiency can appear as a purple discoloration of older leaves. Phosphorus is mobile in the plant, so deficiency symptoms appear first on older leaves. The total phosphorus content of a plant includes all forms of phosphorus in plant tissue.


Potassium is involved in many physiological processes, including protein synthesis and maintaining water balance in the plant. Symptoms of potassium deficiency include reduced growth and yellowing or burning of the edges of leaves. Other symptoms include reduced straw or stem resistance, reduced disease resistance, and reduced winter hardiness of perennial crops. Since potassium is mobile in the plant, symptoms appear first on older leaves. Sandy soils are more likely to be deficient in potassium.


Sulfur is a component of plant proteins. The symptoms of sulfur deficiency may resemble a mild nitrogen deficiency. The only difference is that a sulfur deficiency appears earlier in the newest growth because sulfur is not very mobile in the plant. Sulfur deficiencies are most common in sandy soils with little organic matter. In high precipitation years, sulfur deficiencies can occur in most soil types due to sulfur leaching. Sulfur deficiency is more common in crops such as canola and alfalfa due to higher sulfur requirements.


Calcium is an important part of cell walls. When a soil is limed to an acceptable pH (6.0), calcium is usually adequate. Agricultural lime is composed of calcium and magnesium carbonates (CaCO3 and MgCO3). Applied Ag lime has enough calcium supplied by calcium carbonate (CaCO3) for good plant growth. Areas where calcium deficiencies can occur are irrigated sandy soils with a low pH (<6.0). Symptoms of calcium deficiency include black charred leaf tips and dying growing points because calcium is not mobile in the plant. Boron can cause the same symptoms, but calcium deficiency does not promote the development of side shoots like boron deficiency does.


Magnesium is a key component of chlorophyll and is essential for photosynthesis. Magnesium deficiencies are rare in the Midwest. When a soil is limed to be acceptable, pH (>6.0) for magnesium is usually adequate. Agricultural lime is composed of calcium and magnesium carbonates (CaCO3 and MgCO3). When magnesium deficiencies occur, they are generally associated with irrigated sandy soils with low soil pH (<6.0). Symptoms of magnesium deficiency include mottling of older leaves that proceeds to younger leaves. Interveinal chlorosis begins in the middle of the leaf, and the margins become chlorotic at the end. In some crops, the chlorotic areas of the leaf die and the leaf margins burn.


High levels of sodium are toxic to plant growth. Healthy plant tissue generally contains very little sodium. Symptoms of sodium toxicity include severe growth retardation and loss of support. High sodium in plant tissue is caused by excessive sodium levels in the soil and is usually related to high-sodium water.


Zinc is essential in the production of many plant enzymes. It is also important to balance hormonal levels in the plant. Zinc is moderately mobile in the plant. In some plants, interveinal mottling appears first on older leaves and in others it appears first on new leaves. Interveinal chlorosis can be the same as iron and manganese, except that plants deficient in zinc usually develop exceptionally small leaves. Zinc deficiencies are common in sandy soils with little organic matter. Crops that are sensitive to zinc include edible beans, corn, and potatoes.


Iron is a component of many enzymes in the plant and is essential for photosynthesis. Iron deficiency begins with interveinal chlorosis of the newest leaves and, in severe cases, all leaves show symptoms. Soybeans are susceptible to iron chlorosis and some varieties are more sensitive than others. Iron deficiencies are common in soils that have a high pH (>7.5), or high soluble salts and a high carbonate content (>1.0%). Plant analysis may sometime give very high iron (contamination) readings as a result of dust that normally occurs in plant tissue containing enough iron to contaminate plant samples. Visual symptoms are used to confirm iron deficiency.


Manganese is essential for many reactions in the plant and is essential for the production of chloroplasts. Symptoms of manganese deficiency include interveinal chlorosis in newer leaves. Due to the similarity of the visual manifestations, these symptoms are difficult to distinguish from the symptoms of iron deficiency.


Copper is essential in the formation of enzymes involved in photosynthesis. In wheat, symptoms of copper deficiency include twisting or whitening of the leaf tip. In later stages of growth, blackening of the upper stem and head may occur. Copper deficiencies are common in peat soils (>15% organic matter). Mineral soils with course texture and low in organic matter (<3.0%) may also be copper deficient. A history of manure application increases the chances of copper deficiency. Crops most sensitive to copper deficiency include spring wheat, barley, and winter wheat.


Boron is important in cell division and is essential for the production of amino acids. Symptoms of boron deficiency include browning or browning of new leaf tips and dying growing points similar to calcium deficiency. Lateral shoot growth can occur in boron-deficient plants. Soils likely to be boron deficient are sandy and low in organic matter (<3.0%). Crops most sensitive to boron deficiency include alfalfa and clover.


Chloride is involved in balancing ion charges within the plant, regulating turgor pressure and reducing susceptibility to some diseases. Chloride also participates in photosynthesis. A minor chloride deficiency will show few or no symptoms. When chloride deficiency becomes severe, small necrotic areas will appear on the upper leaves of crops such as wheat. Crops most sensitive to chloride include spring wheat, barley and winter wheat.


High levels of aluminum are toxic to plant growth. Plants that experience aluminum toxicity will have limited root growth, reducing the uptake of phosphorus and several other nutrients. Applying lime to bring the soil pH to 6.0 or higher will eliminate aluminum toxicity. Aluminum is only tested on special request in plant tissue.


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