Productivity and break crop effects of winter-growing oilseeds

Abstract

Productivity, water use and nitrogen (N) use of the oilseeds canola, Indian mustard and linseed were compared with those of wheat and oats in a field experiment in the Riverina. In the following year wheat was grown on the same land and the same attributes were measured. In the first year, wheat productivity exceeded that of all other crops in terms of yield, dry matter production, uptake and the production value (expressed in the common units of the mass of glucose assimilated) of grain and straw. There was no association between productivity and water use, but the cereals had greater canopy cover and, presumably, a greater proportion of the water was transpired rather than evaporated from the soil. In the following year the wheat yield varied with the previous crop species in the order Indian mustard > canola > linseed > oats > wheat. The advantage of the oilseeds to the subsequent wheat crop was evident in terms of shoot density from the stem elongation stage. At the time of maturity, wheat following Indian mustard had extracted more soil water than wheat following canola or wheat following wheat. The early growth advantage to wheat following oilseeds was presumed to be associated with less soil-borne disease. The advantage to wheat following linseed did not persist after anthesis. The advantage to wheat following Indian mustard over wheat following canola appeared to be partly due to greater depletion of subsoil water during the later phases of growth.