Plant Nutrition – The Crucial Importance Of Trace Elements For Your Garden Plants

Most home gardeners are aware that the garden plants require a supply of mineral nutrient for their growth and development. As elements like nitrogen, phosphorus and potassium are the names that usually appear on fertilizer packages, it is sometimes assumed that they are the “important” nutrients. On the other hand, the so-called trace elements, with the possible exception of iron, are often considered to be of negligable importance.

Nothing could be further than the truth. Trace elements like Manganese, Iron, Zinc, and Copper, are every bit as vital to plant metabolism, as they play essential functions in such processes as respiration and photosynthesis, and so a deficiency in even one element will adversely affect the healthy growth of the plant.

Trace elements are called as such because they are required by the plants in miniscule quantities, while the macro elements such as nitrogen are needed and consumed by plants in large quantities. For this reason the latter are sometimes lacking in sufficient amounts, and so have to be supplied artificially by means of chemical or organic fertilizer. Recognising then that the trace elements have to be available to the plants, how can the home gardener ensure that they be so? To answer that, let’s understand a few basic points about trace elements particularly as they apply to dry and Mediterranean climates.

*In the chalky, alkaline soils common to most arid regions, trace elements are normally present in sufficient quantities.

*When present in excessive concentrations however, some are actually poisonous for plants, no more so than the essential element, boron. In fact one of the problems associated with the increasing salinity of dry climate soils, is the rising concentration of trace elements to the point where they are liable to poison garden plants.

*Deficiencies in one or more trace element are most likely to be caused by soil conditions that render the element unavailable to the plants. For instance, in alkaline soils, iron tends to crystallize into a solid state. Due to the fact that plants take up the elements as mineral salts dissolved in the soil water, it follows that in solid form an element cannot be absorbed by the plants’ roots. Poor aeration, typical of many heavy, clay soils is another factor preventing the uptake of essential elements.

*An excess of one trace element in the soil water, (where it is available to be taken up by plant roots) can cause another one to become absorbed by the mineral clay of the soil particles and thus be removed from the soil water. Such is the case with iron, which in high concentrations, “pushes out” manganese and zinc. It follows therefore that iron fertilizers should be used with great caution, as their misuse, is liable to create a deficiency in other minerals.

*In most cases, sound management of the soil should suffice in preventing trace element deficiencies. This entails ensuring adequate drainage and high percentages of organic matter, by way of compost, in the earth. As a result, oxygen levels in the soil rise, and it also becomes less alkaline, thereby increasing the solubility of many mineral salts. In principle, fertilizers which contain trace elements are best reserved for the artificial potting media in use for container culture.

*The most common symptom of iron deficiency is the yellowing of the plants’ foliage – a condition known as chlorosis. Yet these symptoms could alternatively indicate nitrogen deficiency, which can occur under anaerobic soil conditions, even when copious amounts of nitrogen fertilizer are regularly applied. It’s better therefore to try and improve poor conditions such as compacted soil in lawns, before rushing in with iron fertilizer. A soil test may be suitable as well.

*Applying iron fertilizer though is sometimes the answer for plants growing by walls, where building material residues raise the pH (acid-alkaline scale) to a level of alkalinity that prevents iron from dissolving in the soil water. Iron fertilizers normally come in chelate form, which bypass the soil pH. The chelate’s properties of protecting the iron molecules from crystallizing are lost though when exposed to sun light. So the fertilizer has to be dug into the soil as quickly as possible.