脲酶抑制剂与硝化抑制剂对稻田土壤氮素转化的影响

【目的】本研究旨在阐明脲酶抑制剂(urease inhibitor,UI)和硝化抑制剂(nitrification inhibitor,NI)对稻田土壤氮素转化的影响,探讨抑制剂提高稻谷产量以及氮肥利用率的机理。【方法】本试验设在我国南方红壤稻田,共5个处理:1)不施氮肥(CK);2)尿素(U);3)尿素+脲酶抑制剂(U+UI);4)尿素+硝化抑制剂(U+NI);5)尿素+脲酶抑制剂+硝化抑制剂(U+UI+NI);脲酶抑制剂采用N-丁基硫代磷酰三胺(NBPT),硝化抑制剂采用3,4-二甲基吡唑磷酸盐(DMPP)。在水稻分蘖期和孕穗期测定土壤脲酶活性、硝酸还原酶活性、土壤铵态氮含量、硝态氮含量以及微生物碳、氮的含量,分析NBPT与DMPP对水稻两个主要生育期土壤氮素供应的影响,比较各处理的产量以及氮肥利用率,通过逐步回归分析研究以上各指标对产量的影响,探明脲酶抑制剂NBPT与硝化抑制剂DMPP在稻田的增效机理。【结果】1)与单施尿素相比,添加NBPT以及NBPT与DMPP配施均显著提高稻谷产量与地上部氮素回收率,两个处理分别增产6.56%与8.24%,氮素回收率提高幅度为19.4%与23.7%。2)与单施尿素相比,添加NBPT以及NBPT与DMPP配施,显著降低水稻分蘖期的土壤脲酶活性和铵态氮含量,显著提高孕穗期的铵态氮含量,而对此时期的脲酶活性无显著影响,所有处理对两个时期的硝态氮含量、硝酸还原酶活性、微生物量碳、氮含量均无显著影响;因此,NBPT对于抑制脲酶活性以及提高铵态氮含量的作用主要在孕穗期之前,而单施DMPP没有显著效应。3)从各项土壤指标与水稻产量相关性的逐步回归分析结果来看,水稻分蘖期与孕穗期稻田土壤中铵态氮含量对水稻产量影响显著,而且孕穗期的影响大于分蘖期,其余指标则对产量无显著影响。【结论】脲酶抑制剂NBPT以及NBPT与硝化抑制剂DMPP配施显著提高孕穗期土壤中的铵态氮含量,显著提高稻谷产量以及地上部氮素回收率,证明了生产上氮肥后移的重要意义。

Effects of Urease Inhibitor and Nitrification Inhibitor on Nitrogen Transformation in Paddy Soil

【Objective】The research is aimed to reveal the effects of urease inhibitor(UI) and nitrification inhibitor(NI) on nitrogen (N) transformation, and the fertilizer-saving mechanism of inhibitor(s). 【Method】 A field experiment was conducted in the middle and lower reaches of the Yangtze River area, Southern China with a randomized design and five treatments and three replicates: 1) CK (no N fertilizer), 2) U (urea only), 3) U+UI, 4) U+NI, 5) U+UI+NI. NBPT N–(n-butyl) thiophosphoric triamide] and DMPP 3, 4-Dimethyl-1H-pyrazole phosphate] as the urease inhibitor and nitrification inhibitor was uniformly mixed with urea (U) at a rate of 10,000 mg/kg. The total urea, as base fertilizer, was applied to field before the transplanting of rice seedlings. The activities of urease and nitrate reductase, the contents of NH4+-N, NO3--N and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in soil were analyzed in tillering and booting stages. The rice yield and N efficiency were investigated. The mechanism of increased yield and N efficiency due to inhibitor was elucidated by the stepwise regression analysis. 【Result】1) Compared with the normal urea treatment, NBPT addition and NBPT + DMPP significantly improved the grain yields and the recovery of applied N in the above-ground parts by 6.56% and 8.24%，19.4% and 23.7%, respectively. 2) The addition of NBPT and NBPT + DMPP in urea significantly reduced urease activity and soil NH4+-N content at the tillering stage, and increased soil NH4+-N content at the booting stage, without obvious effects on nitrate reductase activity (NRA), soil NO3--N content and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in both stages. There is no significant difference in urease activity between urea and urea + NBPT at the booting stage. Therefore, the urease inhibitor NBPT was effective on inhibiting the activity of urease and improving the content of NH4+ -N before the booting stage. On the contrast, adding DMPP only had no obvious effects on these indexes above. 3)The stepwise regression analysis revealed that the grain yield of rice was significantly associated with NH4+-N content in soil at the tillering and booting stages, especially, the latter. However, other properties in soil have no obvious effects on the grain yield. 【Conclusion】Urea combined with NBPT and combination of NBPT + DMPP slowed down the hydrolytic action of urea and dramatically improved soil NH4+-N content in the booting stage, which is the dominate factor of improving the grain yields and the recovery of applied N in the above-ground parts. The conclusion is consistent with postponing nitrogen technique in agriculture.