I C. Rowland

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This report sets out and summarises data from the Esperance rotation trial.This long-term trial, situated on the Esperance Downs Research Station, looks at various aspects of rotations based on subterranean clover pasture with cereals or sweet lupins as a crop. Data included are yields of the crops both grain and dry matter at anthesis or mid-pod fill also nitrogen content at these two times; pasture production and composition in Spring; clover seed production; weed counts in the crop; soil measurements of total soil nitrogen,organic carbon, mineral nitrogen, pH and extractable potassium are done at thestart of each season.The trial, on Fleming gravelly sand, was commenced in 1968 with linseed as thealternate crop, which was changed to rapeseed in 1971 and to lupins in 1974.Rotations currently operating are a monoculture of wheat and lupins,continuous cropping which alternates lupins with wheat and ley systems of1 year pasture and wheat, 2 years pasture with wheat and lupins or 4 yearspasture with wheat and lupins, with a permanent pasture.Crop yields have shown it was possible to continuously crop using alupin:wheat rotation, however, this was only possible using chemicals tocontrol the annual ryegrass. The buildup in annual ryegrass numbers are shown and there was evidence of development of herbicide resistance in the rye grass of the continually cropped treatments.Yields in a monoculture of cereals have declined with time due to problems with weeds and disease but also due to a reduced soil fertility (as measured by total soil nitrogen and carbon). It was shown that addition of a high rate of ammonium sulphate could restore grain yield to levels near that for wheat grown in rotation with pasture. This was given control of weeds.Calculation of nitrogen fixed by a lupin crop, less the nitrogen removed as seed, showed that in this trial the lupins left sufficient above-ground residues (approximately 77 kg N/ha) to grow the observed grain yield improvement (0.95 t/ha) between a lupin:wheat rotation versus a continuous wheat.

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Western Australia, Farming Systems

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