Effect of nitrogen application strategy in the first cropping rice on dry matter accumulation, grain yield and nitrogen utilization efficiency of the first cropping rice and its ratoon rice crop

The effect of fertilizer application strategy on nitrogen and dry-matter accumulation, grain yield and nitrogen utilization efficiency (NUE) of the ratoon rice crop and its first cropping rice was determined through designing 3 nitrogen applied proportion between basal-tiller dressing and panicle dressing 8∶2(N₁), 7∶3(N₂), 6∶4(N₃) in the first cropping rice season with a constant nitrogen supply at 225.00 kg·hm^-2 in the experiment. The results indicate that N accumulation under N₃ treatment is 9.26% and 3.54% higher at ripening stage of the first cropping rice than that under N₁ and N₂ treatments. Transportation of N from vegetative parts to panicle during grain-filling stage of the first cropping rice under N₃ is separately 21.47% and 6.76% higher than under N₁ and N₂ treatments. For the entire growth period, net dry-matter accumulation in rice under N₃ treatment increases by 5.10% and 4.78% compared with N₁ and N₂. For grain yield of the first cropping rice, N₃ treatment produces the highest (12 431 kg·hm^-2), which is significantly higher than that produced by N₁ and N₂. N utilization efficiency of N₃ treatment is as high 46.44%, 14.81% and 5.43% higher than that under N₁ and N₂. N agronomic efficiency in N₃ treatment is 20.66 kg·kg^-1, 14.97% and 12.34% higher than in N₁ and N₂. Furthermore, the results show that different nitrogen proportion between basal-tiller dressing and panicle dressing with a constant nitrogen supply (225.00 kg·hm^-2 N fertilizer) in the first cropping rice has no significant influence on the ratoon rice crop.