秸秆还田下施氮量对稻茬晚播小麦土壤氮素盈亏的影响

在大田条件下，研究了不同施氮量对秸秆还田下晚播小麦土壤矿质氮含量变化、秸秆氮释放及小麦产量的影响.结果表明： 0～50 cm土层土壤矿质氮含量随着施氮量的增加而显著增加，随生育进程的推进，N₂₇₀和N₃₆₀处理下层土壤的矿质氮显著积累.秸秆氮素释放量随施氮量增加而增加，越冬至拔节期氮释放量最低，拔节至成熟期释放量占总释氮量的50%以上.全生育期施氮量超过180 kg·hm^-2，土壤氮素开始出现显著的盈余，播种至拔节期氮素表观盈余量显著高于拔节至成熟期.籽粒产量在270 kg·hm^-2施氮量下最高, 更高施氮量下氮素利用效率显著降低.施氮量为270 kg·hm^-2时，有利于秸秆全量还田下晚播小麦兼顾产量和生态效益.

Effects of nitrogen application rates on apparent soil nitrogen surplus of late sowing wheat with straw returning in rice wheat rotation.

Field experiments were conducted to study the effects of varying rates of nitrogen application on soil mineral nitrogen content, amount of nitrogen released from the straw, and grain yield of late sowing wheat with straw returning. The result showed that a high nitrogen fertilizer application rate enhanced the mineral nitrogen content in the soil layer of 0 to 50 cm, and also in the lower soil layers when using N at 270 and 360 kg·hm^-2 with the advance of growth stages. The amount of nitrogen released form the straw increased as the nitrogen application rate increased; the lowest appeared from overwintering to jointing, and the highest from jointing to maturity. During the whole growing season, apparent nitrogen surplus occurred when the nitrogen application rate was higher than 180 kg·hm^-2. The N surplus before jointing was significantly higher than that from jointing to maturity. Grain yield reached the highest at a nitrogen application rate of 270 kg·hm^-2, and a higher application rate obviously decreased the nitrogen use efficiency. It could be concluded that applying nitrogen at 270 kg·him^-2 could improve the grain yield of late sowing wheat with straw returning with the optimal ecological benefit.