INFLUENCE OF IRRIGATION AND NITROGEN ON THE YIELD OF RAPESEED (Brasska napus)

Abstract

An experiment was conducted at the agronomy field laboratory of Sher-eBangla Agricultural University, Dhaka-1207 during the period from October, 2005 to Febniary. 2006 to examine the influence of irrigation and nitrogen on the yield of rapeseed (Brassica ;wnzs). There were four different levels of irrigation viz, no irrigation, one irrigation at 30 DAS, two irrigations at 30 and 50 DAS and three irrigations at 30.50 and 65 DAS and four levels of nitrogen viz. 0, 40, 80 and 120 kg N ha''. The experiment was laid out in split plot design with 3 replications assigning irrigation in the main plots and levels of nitrogen in the sub-plots. Irrigation and nitrogen significantly influenced the growth, development, yield and yield attributers of rapeseed. Plant height, thy matter, branches plani'. length of main infloreseenee, number of siliquae in the main intlorescence, siliquae plant', siliqua length, seeds weight of 1000 seeds, seed yield, stover yield. harvest index and oil content were significantly influenced by both irrigation and nitrogen. Among the irrigation treatments, three irrigations- one at 30 DAS (preflowering stage), second at 50 DAS (siliquae formation stage) and another at 65 DAS (siliquac development stage) resulted the greater growth parameters like plant height, dry matter weight and the yield components like branches plant'', length of main inflorescence, number of siliquae in the main infiorescence, siliquae plant', siliqua length, seeds siliqua'. 1000 seed weight, seed yield, stover yield and harvest index. However, irrigation levels influenced the oil content. Three irrigations at 30, 50 and 65 DAS showed the best performance in all respect. The highest seed yield (1455.96 kg ha'') was obtained at three irrigal ions while control treatment gave the lowest yield (348.05 kg ha"). The results revealed that nitrogen at the rate of 120 kg h& showed the best results in all respect except oil content. The highest seed yield (1347.72 kg ha") was obtained at 120 kg N ha' while control treatment produced the lowest yield (408.5 kg ha"). The interaction effect of irrigation and nitrogen revealed that three irrigations one at 30 DAS (pre-flowering stage), second at 50 DAS (siliqua formation stage) and another at 65 DAS (siliqua development stage) in combination with 120 kg N ha'' showed the best performance in most of the cases whereas, the combination effect of control treatments showed the least perfomianee.