DIFFERENTIAL RESPONSE OF WHEAT TO RETAINED CROP STUBBLES .1. EFFECT OF STUBBLE TYPE AND DEGREE OF DECOMPOSITION

Field studies undertaken at Armidale in 1982-84 demonstrated that the principal factors determining the effect of retained stubble on the growth and yield of wheat were the species of the crop from which the stubble had been derived, the amount and distribution of rainfall and the degree of decomposition that the stubble had undergone prior to the next crop. Stubbles were phytotoxic only prior to leaching by rain or decomposition, with unweathered sorghum stubble proving more inhibitory to wheat than unweathered sunflower, field pea, wheat or oilseed rape stubble. The availability of soil nitrate had no influence on the degree of phytotoxicity of any stubble type. Decomposed crop stubbles stimulated wheat growth, with the greatest stimulation recorded in the presence of oilseed rape stubble. © 1990 CSIRO. All Rights Reserved.