Abstract:
With the diversification of the regional crop farming structure, different harvest times for diverse summer crops have prolonged the sowing duration of winter wheat, which significantly affects the stability of grain yield and nitrogen fertilizer utilization. Two sowing patterns (wide-range and drilling sowing) and four sowing dates (3, 10, 17, and 24 Oct., designated as D1, D2, D3, and D4, respectively) were used to investigate the effects of sowing pattern and sowing date on the yield and nitrogen-use efficiency (yield per unit available N, NUE), and to identify a suitable sowing pattern within the prolonged sowing dates, and its theoretical basis. The results showed that, compared with the drilling sowing pattern, wide-range sowing resulted in an average 16.68% greater yield by increasing the numbers of tillers and spikes per unit area. Furthermore, wide-range sowing resulted in an average 16.64% greater NUE by significantly (P<0.05) improving the N uptake efficiency (the ratio of absorbed N to available N, UPE), maintaining or improving the N utilization efficiency (yield per unit absorbed N, UTE). Within each sowing pattern, the spikes per unit area were significantly (P<0.05) decreased and the grain weight per spike was significantly (P<0.05) increased, as the sowing date was delayed. Compared with D1 and D2, the number of spikes per unit area at D3 and D4 with wide-range sowing decreased by 4.26% and 8.46%, respectively, which was much lower than with drilling sowing (6.48% and 14.20%, respectively) (P<0.05). The improved kernel weight per spike at D3 and D4 with wide-range sowing offset the decreased number of spikes per unit area and a stable grain yield was obtained (around 9.00 t/hm2). However, the significant (P<0.05) reduction in number of spikes per unit area with drilling sowing on D3 and D4 resulted in a reduced yield, by an average of 0.34 t/hm2. Within each sowing pattern, the UPE was significantly (P<0.05) decreased and the UTE was significantly (P<0.05) increased, as the sowing date was delayed. Compared with D1 and D2, the UTE at D3 and D4 with wide-range sowing was increased by 9.79% and 19.16%, respectively, which offset the reduced UPE (by 9.98% and 18.47%, respectively); therefore, the NUE was maintained. However, the significant (P<0.05) reduction of UPE at D3 and D4 with drilling sowing resulted in a reduced NUE by an average of 1.01 kg/kg. Compared to the drilling, the wide-range sowing pattern maintained a high grain yield and NUE when sowing relatively late.