SOWING TIME AND TILLAGE PRACTICE AFFECT CHICKPEA YIELD AND NITROGEN-FIXATION .1. DRY-MATTER ACCUMULATION AND GRAIN-YIELD

Mean protein concentrations in wheat (Triticum aestivum) on the Darlin g Downs of southern Queensland have fallen below 10% in recent years, preventing farmers from obtaining 'Prime Hard' status (13.0%) for thei r wheat crop. Two management options, for improving this situation are applications of nitrogenous fertiliser in a wheat monoculture or incl usion of a legume in rotation with wheat. Long-term trials at Warra, o n the western Darling Downs, resulted in the selection of chickpea (Ci cer arietinum) as a useful grain legume cash crop with potential for i mprovement 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 N-2 fixation in c hickpea and the subsequent soil N balance. There were 3 sowing times d uring autumn and winter of each year using conventional tillage (CT). Zero tillage (ZT) was introduced after the first crop for all sowing t imes. 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 wi nter than from sowing in late winter (3.39-3.86 and 0.97-1.22 kg/ha, r espectively). The effects of tillage practice were variable, depending on growth stage. At harvest, ZT plots produced greater total dry matt er yield (4.20 t/ha) and grain yield (1.94 t/ha) than CT plots (3.01 a nd 1.29 t/ha, respectvely), whereas at the time of maximum dry matter, yield was higher under CT for autumn sowings, and under ZT for winter sowings.