The important chain of trace element discoveries was made by numerous agricultural scientists who worked mainly in CSIRO or State Departments of Agriculture. Outstanding in these investigations was the work undertaken by Dr. A. J. Anderson of CSIRO who first showed that acid soils were often deficient in molybdenum.[63] Subsequently it was found in Tasmania, Victoria, South Australia, New South Wales and Western Australia that molybdenum deficiency consistently occurs on podsolic soils derived from sedimentary rocks but is found less commonly on granitic and basaltic soils.

These findings opened the way for the improvement of pastures throughout much of the high rainfall zone of Australia. Even more than that, because molybdenum is essential for the fixation of nitrogen by legumes, its use as a fertilizer had the effect of encouraging clover growth and thus raising the nitrogen levels of what were basically soils of low nitrogen content. In turn this led to the introduction of successful rotational cropping: grazing systems in many localities and to the remarkable conclusion that, in many areas of the temperate high rainfall zone, the application of only 8g/ha of molybdenum constituted the essential basis for profitable crop and animal farming.[64]

The improvement of the environment through the enhancement of soil fertility did not end with such elements as sulphur, potassium, boron, molybdenum, copper, zinc and manganese. The application of lime, a time-honoured practice introduced from Great Britain was found to have a special importance in Australia because it decreased soil acidity, increased the availability of some trace elements, notably molybdenum, and improved the nodulation of clovers by the nitrogen-fixing Rhizobium bacteria. To avoid the need for heavy and costly applications of lime a technique was developed for pelleting clover seed with lime and this has been widely used in pasture establishment.[65]

The famous story of 'sub and super' -the impact on farming of the introduction of subterranean clover, Trifolium subterraneum, coupled with applications of superphosphate as a pasture fertilizer -also had profound effects on the environment. The dramatic and lasting improvements in pasture and animal production and farming profitability due to 'sub and super' have been incalculable and are by no means exhausted. At present some eight million hectares have been sown to improved pastures in areas of adequate rainfall but it has been estimated that, potentially, there is an area of 33 million hectares that could benefit from 'sub and super'.

At the same time as experiments were being carried out on the importance of trace elements in plant nutrition, an equally important series of investigations was being carried out on their importance in animal nutrition.[66] The fact that cobalt is an essential nutrient in the diet of ruminants was first established in 1935 by E. J. Underwood and J. E Filmer[67] in Western Australia and H. R. Marston[68] in South Australia. This discovery led to the identification of cobalt deficient soils and pastures both in Australia and in many other countries of the world, and to methods of their rectification. Because it was found that cobalt was required for the bacterial synthesis of vitamin B₁₂ in the rumen, an ingenious means of ensuring that the bacteria received an adequate cobalt supply was developed in which a clay bullet, rich in cobalt, was administered orally to animals. This lodged permanently in the reticulo-rumen, slowly and continuously releasing the needed amounts of cobalt. The bullet was long-lasting, safe, cheap and effective. Nevertheless it suited many farmers better to apply 'cobaltised' superphosphate as a fertilizer to their pastures and allow the grazing animal to receive its cobalt in its feed. The concept of a slow release nutrient or pharmaceutical device in the rumen has now been used with success in the development of new methods for the release of detergents, magnesium and iodine for the control, respectively, of bloat, hypomagnesaemia and hyperthyroidism. It is also being investigated as a vehicle for administering anti-parasitic drugs.

Australian Academy of Technological Sciences and Engineering