Trace elements are elements that are vital to plant growth but only required in minute amounts. The main TE’s metabolized by plants are Boron, Copper, Iron, Manganese, Molybdenum, Zinc and Chlorine. Their role in plant health is absolutely critical due to the part they play in enzyme systems and chlorophyll production relating to photosynthesis.
Particular trace element deficiencies tend to be associated with soil type. While different pH levels are a contributing factor in the availability of nutrients, a deficiency should not be considered in isolation from other factors. Soil analysis however is generally considered an unsuitable diagnostic tool for finding trace element deficiency because of the very small amounts of material involved. Tissue analysis and identification through visual deficiency symptoms are the main ways of determination. Deficiency symptoms vary dependant on the TE that is lacking however some TE share similar symptoms.
Following are the trace elements and their importance to proper plant nutrition. As a general rule foliar rather than soil applications are used to correct trace element deficiency. Foliar applications are more immediate in their ability to directly deliver the specific elements to the plant.
# Boron is very mobile and readily taken up through the leaf. Boron is necessary for calcium to perform its function in the plant. Plants deficient in boron (usually when pH is above 6.5) have poor development in the growing tips. Boracic acid or Borax (sodium borate) can be applied to counter deficiencies. Application of home-made compost and avoiding the overuse of magnesium sulphate will ensure boron is at a acceptable concentration
# Copper is essential for root formation. It is rare to have a deficiency but may occur in sandy or chalky soils. An application of a copper sulphate based fungicide will rectify this. Copper toxicity causes reduced growth, stunted root development and yellowing of the foliage
# Iron assists in chlorophyll development and function, it plays a role in energy transfer within plants and is a constituent of certain enzymes and proteins. Deficiency causes a yellowing of the leaves and a general lack of vigour. High pH inhibits Fe while low pH makes it more readily available. Iron can be applied using a Manutec product iron chelate which is water soluble or by using Ammonium nitrogen added to the soil.
# Manganese acts in the assimilation of carbon dioxide and electron transfer in photosynthesis and aids in the synthesis of chlorophyll. Manganese deficiencies are similar to iron with yellowing leaves and a lack of vigour, and is generally due to a high pH. The addition of sulphur to lower pH will solve the problem. Mancozeb (fungal spray) is a good source of manganese. Industrial contamination is a major cause of Manganese toxicity.
# Molybdenum is essential to plant growth as a component of the enzymes nitrate and reductase and nitrogenase. If insufficient molybdenum is available nodulation will be retarded and the amount of nitrogen fixed by the plant will be limited. In the unlikely event that molybdenum is scarce foliar sprays of sodium molybdate can be applied.
# Zinc is necessary for starch formation, proper root development and the formation of chlorophyll and carbohydrates. It is involved in photosynthesis and enzyme activity. Depending on the plants deficiency can cause leaf abnormalities, stunting and yellow interveinal chlorosis. Zinc uptake decreases as the soil temperature cools.
# The role of chlorine or chlorine ions in plants is not absolutely clear. Most chlorine is supplied via rain water and growing media will generally have ample amounts of chlorine.
Trace element deficiencies can quite often be misdiagnosed by laboratories. Symptoms may be similar for one or more of the trace elements. “Manutec” have a broad spectrum “Trace element” soluble fertilizer available that is ideal for correcting deficiencies. Sometimes deficiencies may flag larger underlying soil problems which will require more extensive work.