CROPS AND PASTURE ROTATIONS AT COONALPYN, SOUTH-AUSTRALIA - EFFECTS ON NUTRIENTS IN WHEAT AND BARLEY

A crop rotation experiment was conducted at Coonalpyn, South Australia from 1976-1979 on a deep red duplex soil. The experiment studied the effects of grain legumes, pasture or cereal in the previous season on the yield and nutrient content of wheat and barley. Yields, disease assessments, soil nitrogen and water conditions were reported previously. Cereals following grain legumes generally absorbed more of all the nutrients studied, N, P, K, S, Cu, Zn, Mn, than did cereals after pasture; cereal following cereal was generally intermediate. Effects on barley were similar to those on wheat except that wheat took up much more Cu and Mn. Uptake of all nutrients was increased by rainfall, which was greatest in 1979 and least in 1977, but concentrations were often decreased by rainfall. The effects on nutrient concentrations were variable and smaller than on uptake, except for N, Cu and Mn which were much enhanced by grain legumes as the previous crop. Concentrations of trace elements were generally low, being lowest for Cu in 1977, for Zn in 1978 and for Mn in 1979, particularly in barley. Uptake was lowest in 1977, the driest year, especially for Cu. An attempt was made to relate the seasonal effects on levels of trace elements to the pattern of disease incidence.