Trace Plant Nutrients in the Organic Garden

Most gardeners are aware of the major plant nutrients listed on fertilizer packaging: nitrogen (N), potassium (K), and phosphorus (P). However, six other nutrients play a vital role in healthy plant growth. Horticulturists refer to these nutrients as trace elements, because they are needed in such small proportions compared to the major elements.

It’s rare for garden soil to be deficient in iron, manganese, copper, zinc, boron, or molybdenum, but deficiencies can occur when acidic or alkaline soil conditions make the elements unavailable to plants. If a gardener detects a deficiency through a soil test, he can use organic fertilizers and soil amendments to correct the problem.

Iron

Plants need iron to form chlorophyll, which gives healthy foliage its rich, green color. Gardeners may notice an iron deficiency when leaves begin to exhibit yellowing between the veins, especially on new growth. If the soil is too alkaline, plants are at an increased risk for iron deficiencies. Raspberries are especially sensitive to low iron levels. Gardeners can correct an iron deficiency by acidifying the soil with organic matter, such as compost, and fertilizing with liquid seaweed.

Manganese

Sometimes it’s difficult to discern whether a garden has an iron deficiency or a manganese deficiency, as the symptoms are similar. Like iron, manganese plays a role in chlorophyll production. Alkaline soils decrease the amount of manganese available to plants, resulting in yellow leaves and stunted growth. Gardeners must correct any limy soil conditions, and then treat faltering plants with an application of seaweed meal and a side dressing of manure.

Copper and Zinc

Copper and zinc are both necessary to activate enzymes in plants which enable them to produce energy and proteins for growth. Plants deficient in these elements may exhibit small leaves, and will be slow to mature. Gardeners dealing with sandy soil are more likely to experience this than those working in clay soils, but a generous soil amendment of compost usually corrects the problem.

Boron

Boron is necessary for several essential plant functions, including pollen formation and cell wall structure. It’s important to prevent boron deficiencies rather than wait until the problem appears, when it is too late to save the crop. Areas with sandy soils and high rainfalls may experience a leaching of boron from the soil, so stop crop failure by enriching poor soils with organic matter and fertilizing with liquid animal manures.

Molybdenum

A molybdenum deficiency in garden soil is rare, because plants need so little of this element, but overly acidic soil conditions can cause a lack of this mineral. Ailing plants may exhibit whiptail, which occurs when a lack of protein causes leaves to become long and thin. An addition of lime usually corrects molybdenum deficiencies in the garden.

Source:

University of Minnesota Extension