Fertilization affects soil nitrogen cycling and nitrous oxide (N2O) emissions, which are mainly driven by microbes. A 32-year field experiment was conducted to investigate the effects of chemical fertilizers and their combination with organic materials on the abundance of denitrifying functional genes (nirS, nirK, nosZ I and nosZ II) in Ultisol. The treatments comprised no fertilizer (CK), chemical fertilizer, chemical fertilizer+peanut straw, chemical fertilizer+rice straw, chemical fertilizer+radish and chemical fertilizer+pig manure. Compared with the single chemical fertilizer treatment, soil pH and organic carbon content increased in the chemical fertilizer plus organic material treatments, with chemical fertilizer+pig manure having the strongest effect. Long-term fertilization did not affect the abundance of nirK gene, but significantly altered the nirS gene abundance. Compared to CK, long-term chemical fertilizer application increased the abundance of nirS gene by 426%. However, partial replacement of chemical fertilizer by organic materials decreased the abundance of nirS gene. The abundance of nosZ I gene was one order of magnitude higher than that of nosZ II, indicating the domination of nosZ I in the acidic Ultisol. Long-term fertilization did not affect the abundance of nosZ II, whereas chemical fertilizer+pig manure increased the abundance of nosZ I by 138%. Results of stepwise regression analysis showed that available phosphorus content was the primary factor regulating the abundance of nosZ I gene, whereas the abundance of the nosZ II gene was mainly regulated by nitrate content. Moreover, the lowest (nirS+nirK)/(nosZ I+nosZ II) value in the chemical fertilizer+pig manure treatment indicated that long-term manure application might reduce N2O emission potential in Ultisols.
农田施肥会影响土壤微生物驱动的氮素转化和氧化亚氮(N2O)排放。基于32年的长期肥料定位试验,研究了旱地红壤反硝化功能基因(nirS、nirK、nosZ I和nosZ II)对不同长期施肥处理的响应及其关键影响因素。试验包括6个处理,分别为不施肥(CK)、单施化肥、化肥+花生秸秆、化肥+水稻秸秆、化肥+萝卜菜和化肥+猪粪。结果表明: 与单施化肥相比,化肥和有机物料配施可以有效缓解红壤酸化、提高土壤有机碳含量,其中以化肥和猪粪配施的效果最好。长期施肥对nirK基因丰度没有显著影响,但显著影响nirS基因丰度;与CK相比,长期单施化肥可显著增加nirS基因丰度,增幅达426%,但与单施化肥相比,化肥和有机物料配施降低了nirS基因丰度。旱地红壤中nosZ I基因丰度远高于nosZ II基因丰度,表明nosZ I在酸性红壤中占主导地位;长期施肥对nosZ II基因丰度没有显著影响。但长期施用化肥+猪粪显著提高了nosZ I基因丰度,增幅为138%。逐步回归分析表明,有效磷含量是影响nosZ I基因丰度的关键环境因子,而nosZ II基因丰度则主要受硝态氮含量的影响。化肥和猪粪配施处理的(nirS+nirK)/(nosZ I+nosZ II)值最低,表明化肥和猪粪配施可能会降低旱地红壤的N2O排放能力。.
Keywords: Ultisols; denitrifiers; long-term fertilization; nosZ I; nosZ II.