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Mean protein concentrations in wheat (Triticum aestivum) on the Darling Downs of southern Queensland have fallen below 10% in recent years, preventing farmers from obtaining 'Prime Hard' status (13.0%) for their wheat crop. Two management options, for improving this situation are applications of nitrogenous fertiliser in a wheat monoculture or inclusion of a legume in rotation with wheat. Long-term trials at Warra, on the western Darling Downs, resulted in the selection of chickpea (Cicer arietinum) as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield, N accumulation and N2 fixation in chickpea and the subsequent soil N balance. There were 3 sowing times during autumn and winter of each year using conventional tillage (CT). Zero tillage (ZT) was introduced after the first crop for all sowing times. Greater total dry matter yield and grain yield (4.18-5.95 and 1.63-2.25 t/ha, respectively) resulted from sowing in autumn or early winter than from sowing in late winter (3.39-3.86 and 0.97-1.22 kg/ha, respectively). The effects of tillage practice were variable, depending on growth stage. At harvest, ZT plots produced greater total dry matter yield (4.20 t/ha) and grain yield (1.94 t/ha) than CT plots (3.01 and 1.29 t/ha, respectively), whereas at the time of maximum dry matter, yield was higher under CT for autumn sowings, and under ZT for winter sowings. |
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