Keywords: Micronutrients, Field crops, Boron, Copper, Manganese, Zinc.

Micronutrients may be needed in quantities as little as a few grammes per hectare but adequate supplies are essential if crop yield and quality are not to suffer. Of the eight micronutrients known to be essential for crops, four are frequently applied to field crops in Europe: boron, copper, manganese and zinc. In addition, selenium is applied to increase concentration in the crop and so the quality of livestock or human diets. The grower faces problems in identifying a particular deficiency from crop symptoms. Sometimes, where a deficiency is sub-clinical or where only crop composition is affected, only chemical analysis of plant tissues will identify the problem. The grower therefore needs to be aware of known influencing risk factors such as soil pH, organic matter content, parent material and crop species. The cost of micronutrient application is low relative to those of major nutrients or to the value of the crop. There will be an incentive towards crop treatment even where the perceived risk of a deficiency is low. Nevertheless, awareness of the risk factors and, where necessary, analysis of crop tissue or soil should help to restrict applications to deficient crops.

Ian R Richards, MSc, PhD., Ecopt, Bredfield, Suffolk, UK.

22 Pages, 1 Table, 84 References.