Micronutrients Affecting Plants

Sources

• The two sources of micronutrients in healthy soil are minerals and organic matter (humus). Mineral content results from the breakdown of rocks as soil is formed. Organic matter forms from decomposing plant and animal life in the soil. Micronutrients are released from the decaying animal and vegetative matter and become part of the soil. Soil with organic matter content below 2 percent has fewer micro-nutrients available to plants. Soils that have high organic matter content -- over 30 percent -- are also likely to be low in micronutrient availability to plants. Soil pH levels -- the acid and alkalinity ratio -- affect how plants absorb micronutrients. Soils with high pH levels have fewer available nutrients.

Compost

• Backyard compost made from kitchen peelings, yard clippings, newspaper scraps and leaves is a reliable source for boron and all the other micronutrients. Synthetic fertilizers supply the macronutrients nitrogen, phosphorus and potassium but do not supply micronutrients. The first symptom of boron deficiency in soil is death of the growing tips of plants and failure to set flowers. Sulfur and manganese deficiencies cause yellowing in the leaves. Boron deficiency may cause rust-colored cracks on the stem, and zinc deficiency causes puckered leaf margins. Molybdenum in the soil is essential for plants to retain nitrogen. Stunted growth may also be the result of soil deficiencies in micronutrients.

Magnesium and Calcium

• Magnesium is necessary for plants to make use of nitrogen, which is their main growth stimulant. Deficiency symptoms include stunted growth and dead spots or patches. Magnesium is also essential for the movement of starches and sugars through the plant, which provide material for growth. The micronutrient calcium stimulates root growth, promotes thick stems and supports the transportation of other nutrients through the plant. Deficiency symptoms are stunted root growth, distorted leaves and blossom rot. Calcium is also necessary for plants to utilize nitrogen.

Copper and Iron

• The first iron deficiency symptoms on a plant may be yellowing between the veins of young leaves. Iron is essential for the development of chlorophyll, which produces a green color. Soil with high pH readings may restrict the uptake of iron. Copper is the micronutrient that helps a plant use enzymes. It also helps plants reproduce. Copper is not readily transferred from old to young leaves, so deficiencies appear first in new leaves as yellowing. Slightly stunted or misshapen growth also results from a copper deficiency.