تأثیر کود نیتروژن و تاریخ نشاءکاری بر عملکرد، اجزای عملکرد و خوابیدگی ساقه برنج در منطقه اصفهان

In order to investigate the effect of nitrogen (N) fertilizer and transplanting date (TD) on yield, yield components and stem lodging of rice (Oryza sativa), a two-year study (2007-2008) was carried out in Fozveh Research Station, Agricultural and Natural Resources Research Center of Isfahan, Iran, using split plots, based on randomized complete blocks design with three replications. Four N fertilizer levels (control, 126, 180 and 234 kg/ha N) were assigned as the main factor and three TDs (late May, early June and late June) were assigned the sub-factor. The results showed that application of 126 and 180 kg/ha N caused 13 and 17% increase in the yield, respectively, as compared to control. But, the 234 kg/ha N treatment had similar yield to control treatment (6672 kg/ha), due to severe stem lodging (45%). The highest agronomic N efficiency (17.7 kg of grain produced per kg of consumed N) was obtained in the 180 kg/ha N treatment, and this was not significantly different from the 126 kg/ha N treatment. Number of panicles per m2 in 126 and 180 kg/ha N treatments, was increased by 16 and 24%, respectively, over the control treatment. Transplanting the seedlings to the main field in late May and early June produced a yield of 7391 and 7831 kg/ha, respectively. Although the stem lodging in late June was lower than the other two TDs, but grain yield was reduced by 29 and 37% with respect to late May and early June, respectively. The results showed that application of 126 kg/ha N and transplanting the seedlings in late June is recommendable for Sazandegi rice cultivar in Isfahan region.