控释尿素减施对双季稻田径流氮素变化、损失及产量的影响

为了探究双季稻田典型自然降雨径流过程中氮(N)的输出特点,采用田间径流池法,通过长期田间定位试验,比较普通尿素(U)和控释尿素(CRU)减施稻田径流水中总氮(TN)、铵态氮(NH_4~+-N)和硝态氮(NO_3~--N)的动态变化及N素径流流失量和流失率。结果表明:稻田施肥初期出现N素径流峰值,是防控N素径流损失的关键时期。早、晚稻季生育期间施N处理径流水中以NH_4~+-N为主要形态,分别占TN径流损失量的64.5%~66.3%,61.0%~68.6%。早、晚稻季U处理径流水TN流失量(率)分别为5.6(2.2%),5.0(1.7%)kg/hm~2;CRU处理较U处理径流水TN流失量分别降低17.4%~34.1%,17.3%~37.7%;且随着N肥用量的减少,TN流失量(率)逐渐降低。受降雨强度的影响,早稻季N素径流损失较晚稻季高,且晚稻季CRU处理N素径流损失减排效果优于早稻季。早、晚稻季及连作周期CRU处理TN径流累计损失量和籽粒产量与施N量呈显著线性关系,随着N用量的增加而增加。总之,U处理显著提高径流水中N素浓度以及NH_4~+-N占TN的比例。CRU处理有效减缓N素释放速度,降低施肥初期N素径流损失量,实现增产;而CRU减施有利于进一步防控稻田N素流失风险,促进农业面源污染减排,且以减N 10%效果较好。

Effects of Controlled-release Urea Application on Dynamics and Loss of Nitrogen in Runoff and Yield in Double-rice Cropping Field

In order to explore nitrogen (N) output characteristics in double-rice cropping field during the process of the typical natural rainfall runoff, the long-term experiment with common urea (U) and reduction of controlled-release urea (CRU) was conducted to study the dynamics of total nitrogen (TN), ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^--N) loss and loss ratio of runoff in paddy field. The results showed that N loss peaked in the early time of fertilization, which was the critical period to control N loss. NH₄⁺-N was the main form of N-applied treatments to runoff during early and late rice season, accounting for 64.5%~66.3% and 61.0%~68.6% in TN loss, respectively. The TN loss and loss ratios of runoff in U treatment during early and late rice season were 5.6 kg/hm² (2.2%), and 5.0 kg/hm² (1.7%), respectively. Compared with U treatment, TN loss in CRU treatments were reduced by 17.4%~34.1% and 17.3%~37.7%, and the TN loss and loss rates of runoff decreased with the decrease of N fertilizer rate. N loss in early rice season was higher than that in late rice season, and the inhibition of CRU treatments in N loss in late season rice was better than that of early rice season as affected by rainfall intensity. TN loss and grain yield in CRU treatments for earlyseason, late-season rice and the continuous cropping cycle had significant linear relationships with N fertilizer rate, which increased with the increasing N fertilizer rate. In conclusion, U treatment significantly increased N concentration and the ratio of NH₄⁺-N to TN in runoff. CRU effectively reduced N release rate and N loss in the early time of fertilization, and thus increased grain yield. The findings indicate that the reduction of CRU is helpful for further control of N loss risk in paddy field, and promote the reduction of agricultural non-point source pollution, especially in reduction of 10% N treatment.