The occurrence and correction of boron deficiency

Positive responses to B application, which provide clear evidence of B deficiency, have been reported in over 80 countries and on 132 crops over the last 60 years. It is estimated that about 15 million ha are annually treated with B. In a few regions in the world, B deficient soils exist over a wide area, as for example in eastern and southern China. Elsewhere B deficiency is restricted to particular soil types and crops. Acrisols and Podzols and to a much lesser extent Andosols, Luvisols and Ferralsols, appear to be the soil groups most likely to produce B deficient crops. Soil parent material and texture are considered to be the major soil factors associated with the occurrence of B deficiency. For many crops it is the B requirement for successful fertilisation that is of critical importance; even crops with a small B requirement, such as the cereals, can suffer impaired seed set due to B shortage at a critical time. Climate, particularly high light intensity and low temperature are factors that need to be considered in relation to the occurrence of B deficiency. Boron deficiency can be readily prevented and corrected by both soil and foliar applications. Most reliance is placed on refined sodium borates, but crushed ores are used both in the manufacture of boronated fertilisers and on their own. Depending on the ore, its particle size and method of application, B supply may be extended by using an ore which dissolves slowly.