~(15)N示踪的水稻氮肥利用率细分

以粳稻武运粳23和超级杂交籼稻Y两优2号为供试品种,应用15N示踪方法研究不同时期施肥对水稻不同阶段氮肥利用率的影响,以确定不同时期施肥的最佳阶段氮肥利用率。结果表明,基肥在基肥阶段(移栽后的8 d左右)的吸收利用较低,2012年水稻基肥氮(15N)吸收量不到5 kg hm–2,2013年最大为7.5 kg hm–2,回收利用率在1.5%~11.5%之间;基肥主要是在蘖肥阶段(分蘖肥与穗肥之间)被吸收,其回收利用率在6.6%~24.9%之间,平均为15.6%;穗肥阶段(穗肥后到成熟)基本不再吸收基肥。基肥氮的总体恢复利用效率不高,在9.1%~22.8%之间,品种及氮肥运筹对基肥氮的总体恢复利用效率影响不显著。蘖肥主要在蘖肥阶段发生作用,施穗肥后水稻基本不再吸收蘖肥。蘖肥的总体恢复吸收利用率和基肥相当,在17%~34%之间,Y两优2号高于武运粳23。穗肥的回收效率最高,在54.0%~82.1%之间,武运粳23低于Y两优2号。水稻在整个生育期的总体氮肥恢复效率随氮肥用量的增加而下降,变化在32%~64%之间。水稻一生中吸收积累的氮素中,基肥的贡献占4.13%~10.59%(平均6.92%),蘖肥占3.98%~11.75%(平均7.58%),穗肥占13.32%~37.56%(平均26.02%),土壤的贡献在45.71%~70.83%(平均59.91%)之间。基蘖肥用量越大,其损失也越大,总体氮肥利用率也越低。研究结果证明,在水稻氮肥管理中必须考虑水稻各阶段对不同时期施肥的吸收利用情况,从而提高水稻氮肥利用效率,保证产量的同时减少不必要的损失。

Subdivision of Nitrogen Use Efficiency of Rice Based on 15N Tracer

The nitrogen (N) uptake, and N use efficiencies (NUE) at different rice growth stages (i.e. during basal, tillering and panicle fertilizations) were studied using ¹⁵N isotope tracing. A two-year field experiment with two N rates and two distribution ratios was conducted using two different high-yielding rice cultivars Wuyunjing 23 (japonica) and Yliangyou 2 (hybrid indica). A sub-plot of ¹⁵N isotope tracing experiment with three duplications under the same treatment was also set up in the field. The results revealed that basal nitrogen absorbed by rice was only 1.5%–11.5% before tillering fertilization (eight days after transplanting), 6.6%–24.9% from tillering fertilization to panicle fertilization, and little after panicle fertilization. The overall recovery efficiency of basal N (NUE_B) was low and ranged from 9.1% to 22.8%, not significantly affected by different cultivars and N treatments. Tillering fertilizer N was mainly absorbed from tillering fertilization to panicle fertilization, and no longer had effect after panicle fertilization. NUE of tillering N fertilizer (NUE_T) was 17%–34%, which is almost the same as that of basal fertilizer. NUE_T of Yliangyou 2 was higher than that of Wuyunjing 23. Compared with basal and tillering N fertilizers, NUE of panicle N fertilizer (NUE_P) was the highest with a value of 54.0%–82.1%, and Wuyunjing 23 had lower NUE than Yliangyou 2. The whole NUE in the entire growth period of all N fertilizers decreased with the increase of N application rate, and varied from 32% to 64%. Among the total N uptake of rice, the contribution was 4.13%–10.59% (average 6.92%) for basal N fertilizer, 3.98%–11.75% (average 7.58%) for tillering fertilizer, 13.32%–37.56% (average 26.02%) for panicle fertilizer, and 45.71%–70.83% (average 59.91%) for the soil. The experiment also revealed that the more the basal and tillering fertilizers applied, the lower the total NUE. It is suggested that rice N management, the N absorption and utilization from fertilizer applied at different stages should be considered to improve the NUE of rice, and ensure the hig yield while avoid the N loss.