Superphosphate on wheat: Influence of previous level of application on current response

Abstract

Over eight cycles of a wheat-oats-fallow rotation, the current effect of superphosphate was shown to decrease at an increasing rate as the level of previously applied superphosphate was increased. This relationship did not continue when the rotation was changed to a wheat-pasture-pasture-fallow system for three further cropping cycles ; despite high levels of previously applied superphosphate current effect was frequently greater than on virgin soil.