Response of super hybrid rice “Y Liangyou No. 1” to N-fertilizer dose and its N use efficiency

Six doses of N 0 kg·hm^-2 (N0), 90 kg·hm^-2 (N1), 135 kg·hm^-2 (N2), 180 kg·hm^-2 (N3), 225 kg·hm^-2 (N4) and 270 kg·hm^-2 (N5) were used to compare grain yield composition and N use efficiency of “Y Liangyou No. 1” super hybrid rice. Based on the model of N dose-yield, yield is highest (11.42 t·hm^-2) at N application rate 245.9 kg·hm^-2. On the other hand, economic benefit is highest at 213.5 kg·hm^-2 N amount due to the harmony between rice yield and N use efficiency. A Logistic model was used to simulate dynamic of total biomass production under different N doses. Though there exist different models for different N doses, total biomass generally increases rapidly at grain-filling stage. With increasing N dose, N recovery efficiency (NRE) and N agronomic efficiency (NAE) continuously decrease, but at different degrees. However, N4 treatment gives the best conditions for N dose, grain yield and N-fertilizer use efficiency. It has the highest yield and N-fertilizer use efficiency. As 20% total N dose for earing fertilizer does not meet grain-filling requirement, it is suggested to increase N application rate at booting stage of super hybrid rice cultivation.