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.
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