The addition of trace elements to fertiliser is a well accepted method of overcoming deficiencies in plants and animals in New Zealand. Cobalt sulphate, for instance, is commonly added to fertiliser to prevent Co deficiency in grazing animals. New Zealand farmers annually apply 130 tonnes of cobalt sulphate to permanent pastures at rates up to 350g/ha/annum. Cobalt deficiency is normally diagnosed by the analysis of animal tissues or plant material. Soil Co analyses have traditionally been considered unsatisfactory for diagnostic purposes. Research, however, suggests that the relationship between soil and plant Co for particular soils is sufficiently promising to consider using soil Co analysis as an advisory tool for predicting the likely Co status of pasture. Soil Co “reserves” can then be modified by fertiliser Co usage to provide conditions which will minimise the likelihood of Co deficiency occurring in grazing animals
