Micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn).
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The 7 micronutrients are sufficient in most soils to meet crop needs. However, some sandy soils and other low-organic matter soils are naturally deficient in micronutrients, and high pH soils may make some micronutrients less available and therefore deficient. In the major crops and production areas of North America, the micronutrients most often supplied by fertilization include zinc, manganese, boron and iron. Basic chemical properties of micronutrients help determine their availability in soils
Because of complex chemical reactions within the soil, micronutrient availability is ultimately controlled by the equilibrium between the soil solution, soil organic matter, cation exchange sites, and insoluble compounds of micronutrients. Soil acidity or alkalinity has a large effect on the tie-up of micronutrients or their availability to plants. Micronutrients are most available in acid soils and often unavailable at high pH.
Organic Matter
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Organic matter is a reservoir for essential plant nutrients, continuously supplying these nutrients to the crop as it decomposes over time. This reservoir is especially important for anions such as boron, which do not bind to soil particles and are therefore subject to losses. Soils that receive regular additions of organic residues such as manures rarely show micronutrient deficiencies. An exception is deficiencies caused by nutrient imbalances, such as a deficiency of manganese caused by an excess of phosphorus in overly manured soils. Another exception is soils of extremely high organic matter such as muck or peat soils. In these soils, strong, natural chelation (the combination of a micronutrient with an organic molecule) can make some micronutrients unavailable, particularly copper, manganese and zinc
Functions of Micronutrients
Micronutrients differ in the form they are absorbed by the plant, their functions and mobility in the plant.
Boron
Important in Sugar transport, cell division and amino acid production.
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Chloride
Used in resisting decease, and photosynthesis reaction.
Copper
Component of enzyme Involved in photosynthesis.
Iron
Components of enzyme involved in chlorophyll synthesis and photosynthesis.
Molybdenum
Involved in nitrogen metabolism, essential in nitrogen fixation by legumes.
Manganese
Chloroplast production, cofactor in many plant reaction, activates enzymes.
Zinc
Components of many enzymes, essentials for plant hormone balance and auxin activity.
