Optimization of Irrigation and Nitrogen Regimes for Rapeseed Production Under Drought Stress
In order to optimization of irrigation and nitrogen management for rapeseed (Brassica napus L. cv. Hyola 401) production at terminal drought stress, an experiment was conducted in a split plot at base of RCB design with four replications in experimental field of Agricultural and Natural Resource University of Ramin during 2005-2007. Irrigation management at three levels: without stress, moderate and severe water stress established as main plots and four N fertilizer rates: 90, 140, 190 and 240 kg N ha-1 were consider as sub plots. The results showed that rapeseed oil and grain yield was affected by terminal drought stress severely. Moderate and severe drought stress reduced grain yield by 14.5 and 32% compared to no stress condition, respectively. With increasing of N rate the number of branches, pod m-2 and 1000-seed weight and consequently seed yield was increased significantly. Seed oil content adverse to seed protein content with increasing the severity of drought stress was decreased. Increase in nitrogen led to increase in protein content, but oil content was decreased. Highest seed and oil yield (3996.3 and 1803.9 kg ha-1, respectively) with 190 kg N ha-1 at no stress condition was obtained. According to these results for maximize production of rapeseed in this region and probably in similar conditions full irrigation and application of 190 kg N ha-1 (with respect to soil analyze) was recommended.
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