Effect of different crops rotation with rice, N rate and N split application on crop grain yield

To evaluate the effect of previous crop, N rate and N split application on rice (Oryza sativa L. cv. Hashemi) growth and paddy yield, a field experiment was conducted at SowmaehSara, Guilan province, in 2014 as a split-factorial arrangement based on Randomized Complete Block Design with three replicates. Main plots were previous crop [Berseem clover, faba bean, and control (fallow)] and subplots were the factorial arrangement of N rate (50, 75, and 100 percent of N recommended rate which was 50, 75 and 100 kg Urea ha-1, respectively) and N split application (100 percent at transplanting stage, 100 percent at tillering stage, and 50 percent at transplanting stage and 50 percent at panicle initiation). Results showed that rice paddy yield was significantly affected by previous crop and N rate, but N split application had no significant effect on paddy yield. The highest paddy yield (4142.8 kg ha-1) was obtained when rice was cultivated after berseem clover and the lowest paddy yield (3494.0 kg ha-1) was obtained when rice was cultivated after faba bean. Rice paddy yield was increased significantly by 8% as N application rate increased from 50 to 78 kg urea ha-1, but further increase in N rate (100 kg urea ha-1) had no significant effect on paddy yield. Based on the result of this experiment, the highest rice paddy (4142.8 kg ha-1) was obtained when rice was cultivated after berseem clover and N was applied at the rate of 75 kg urea ha-1.