improving water productivity and optimal time and amount of single irrigation for rainfed spring rapeseed

in order to investigate the effects of single irrigation amounts at different stages of rapeseed growth on yield and the improvement of water use efficiency and water productivity indices, this experiment was conducted as split plot arranged in a randomized complete block design (rcbd) with three replications during 2002-2003 for rainfed spring rapeseed variety (pf.7015.91= sarigol) at maragheh agricultural research station of dari. the treatments included four levels of single irrigation amounts (rainfed, 30, 60 and 90mm of water use) at three growth stages (stem elongation, flowering and filling stage). the analysis of variance showed that, during two seasons of the study, there were significant effects due to single irrigation amounts, growth stages and their interactions. results showed that the optimum level of single irrigation for increase and yield stability of rapeseed was 60mm water use at flowering stage which produced 1071kg.grain.ha-1. the wpi+p, wpi and wue for this treatment were 4.79, 8.09 and 2.46kg.mm-1, respectively.