氮素抑制剂对双季稻产量、氮素利用效率及土壤氮平衡的影响

【目的】了解氮素抑制剂对双季稻产量、氮素利用效率及氮素在土壤中转化的影响，旨在为制定科学合理的农田氮素管理措施及节肥增效策略提供依据。【方法】以湘早籼45号和荆楚优148为材料，于2015年早、晚稻期间进行田间试验。试验设5个处理:不施肥 (CK)；100%尿素 (100%U)；80%尿素 (减氮20%，80%U)；80%尿素+脲酶抑制剂NBPT (80%U+NBPT)；80%尿素+硝化抑制剂DCD (80%U+DCD)。研究尿素减施条件下添加硝化抑制剂 (NBPT) 和脲酶抑制剂 (DCD) 对双季水稻产量、氮素养分吸收利用效率、土壤硝态氮、铵态氮、微生物量氮及土壤氮平衡的影响。【结果】NBPT和DCD均有利于提高早、晚稻产量、植株氮吸收量和氮素利用效率。减氮20%条件下添加NBPT(80%U+NBPT)处理早、晚稻稻谷较100%尿素处理 (100%U) 分别增产5.0%和6.1%，较施用80%尿素 (80%U) 分别增产8.0%和14.0%；80%U+DCD与100%U处理的早、晚稻稻谷产量差异不显著，较80%U处理分别增产6.0%和4.2%。80%U+NBPT较100%U处理早、晚稻植株氮吸收量分别增加4.5%和9.4%，较80%U处理分别增加10.3%和16.2%。80%U+NBPT和80%U+DCD处理氮肥表观利用率、氮肥农学效率、氮肥偏生产力和氮素吸收效率均较100%U和80%U处理提高。添加NBPT和DCD降低了早、晚稻收获后土壤硝态氮和铵态氮残留量，显著提高土壤微生物量氮积累量，降低氮表观损失，有利于维持作物-土壤体系氮素平衡。早、晚稻收获后80%U+NBPT较100%U处理氮表观损失降低42.2%和44.6%，较80%U处理降低27.5%和29.2%，80%U+DCD较100%U处理降低23.7%和31.6%，较80%U处理降低4.2%和12.6%。【结论】在该区域双季稻种植体系中，氮肥减量20%条件下添加NBPT和DCD能增加或维持水稻产量，提高氮素利用效率。供试条件下，添加NBPT提高氮素持续供应能力和保持土壤氮素平衡的效果好于DCD。

Effects of urease and nitrification inhibitor on yield,nitrogen efficiency and soil nitrogen balance under double-rice cropping system

【Objectives】The effects of nitrogen inhibitor on yield and nitrogen use efficiency of rice were studied in this paper, aiming to formulate scientific nitrogen management of saving fertilizer and improving fertilizer usage efficiency, as well as keep the balance of soil nitrogen.【Methods】A double-rice field trail was conducted in early and late rice season in 2015 using rice cultivars of Xiangzaoxian 45 and Jinchuyou 148 as test materials. Five treatments were designed as follows: 1) No fertilizer (CK); 2) 100% urea (100%U); 3) 80% urea (80%U); 4) 80% urea plus urease inhibitor NBPT (80%U+NBPT); 5) 80% urea plus nitrification inhibitor DCD (80%U+DCD). The double rice yields, nitrogen uptakes were investigated, and the nitrogen use efficiencies and the balance of some fractions of soil nitrogen were calculated.【Results】Addition of NBPT or DCD into urea could increase the yield and nitrogen absorption of rice. The early and late rice yields in 80%U+NBPT treatment were 5.0% and 6.1% higher than those in 100%U treatment, and 8.0% and 14.0% higher than those in 80%U treatment; the early and late rice yields in 80%U+DCD treatment were 6.0% and 4.2% higher than those in 80%U treatment, similar to those in 100%U treatment. The accumulations of nitrogen by rice plant in 80%U+NBPT treatment in early and late rice were 4.5% and 9.4% higher than those in 100%U treatment, and 10.3% and 16.2% higher than those in 80%U treatment. Apparent use efficiency of nitrogen fertilizer, agronomic efficiency of nitrogen fertilizer, partial factor productivity of applied nitrogen fertilizer and nitrogen uptake efficiency by plant in both 80%U+NBPT and 80%U+DCD treatments were all significantly improved compared with 100%U and 80%U treatments. Adding NBPT or DCD effectively reduced soil nitrate nitrogen and ammonium nitrogen contents, and significantly increased soil microbial biomass nitrogen after harvest of early and late rice. At harvesting stages, the apparent nitrogen loss in early and late rice fields in 80%U+NBPT treatment were 42.2% and 44.6% lower than in 100%U treatment and 27.5% and 29.2% lower than in 80%U treatment; the apparent nitrogen loss in 80%U+DCD treatment were 23.7% and 31.6% lower than in 100%U treatment and 4.2% and 12.6% lower than in 80%U treatment.【Conclusions】Adding urease inhibitor NBPT or nitrification inhibitor DCD to urea and reducing 20% of urea input could increase or keep the same levels of rice yields, enhance nitrogen use efficiency. Under the experimental condition, the effects of NBPT in increasing nitrogen supply and keeping soil nitrogen balance are better than those of DCD.