长期施肥旱地土壤易分解与耐分解氮的矿化特性

Mineralization Characteristics of Upland Soil Labile and Recalcitrant Nitrogen Under Long-Term Different Fertilization Systems

【目的】土壤易分解氮库和耐分解氮库是土壤有机质的重要组分,其矿化能力的大小可反映土壤有机氮的周转性能。论文旨在研究长期不同施肥制度下土壤易分解氮库与耐分解氮库的矿化特性,为了解不同培肥措施及其氮素供应提供依据。【方法】以中国长期不同施肥处理的2种旱地土壤(黑土和潮土)为例,选取不施肥(CK)、单施化肥(NPK)、化肥配施秸秆(NPKS)和化肥配施有机肥(NPKM)4个处理,采用颗粒密度法,将土壤有机氮分为易分解氮和耐分解氮2个组分,室内培养分析不同组分氮的矿化特性。【结果】筛分及培养结果显示,黑土和潮土的平均质量回收率和氮回收率均超过97%,易分解和耐分解氮组分矿化量之和占原土矿化量的平均比例为99.91%(99.89%—99.93%),是一种研究土壤易分解和耐分解氮组分矿化特性的可行方法。2种旱地土壤NPK、NPKS和NPKM处理易分解氮组分净氮矿化潜势(除黑土NPK处理差异不显著)较CK处理显著提高26.82%—137.10%;不同施肥处理对旱地黑土、潮土易分解氮组分净氮矿化潜势影响显著,其中,黑土NPKM处理易分解氮组分净氮矿化潜势为1.48 mg·kg-1·d-1,显著优于NPKS(1.02 mg·kg-1·d-1)与NPK(0.75 mg·kg-1·d-1)处理;潮土NPKM处理易分解氮组分净氮矿化潜势为1.17 mg·kg-1·d-1,显著优于NPKS(0.89 mg·kg-1·d-1)与NPK(0.76mg·kg-1·d-1)处理;旱地土壤各处理耐分解氮组分净氮矿化潜势之间差异不显著,其中,黑土各处理耐分解氮组分平均净氮矿化潜势为0.58 mg·kg-1·d-1(0.52—0.63 mg·kg-1·d-1),潮土为0.51 mg·kg-1·d-1(0.40—0.62 mg·kg-1·d-1)。不同施肥处理旱地黑土、潮土易分解氮组分净氮矿化潜势均显著大于同处理耐分解氮组分净氮矿化潜势,NPKM处理两者显现出最大差异,其中,黑土易分解氮组分净氮矿化潜势是同处理(按CK、NPK、NPKS、NPKM顺序)耐分解氮组分的1.41、1.39、1.75和2.35倍,潮土易分解氮组分净氮矿化潜势是同处理(按CK、NPK、NPKS、NPKM顺序)耐分解氮组分的1.22、1.33、1.56和1.87倍。土壤矿化过程中易分解组分对原土矿化贡献率受施肥措施显著影响,其大小按CK、NPK<NPKS<NPKM顺序递增,黑土依次为10.82%、12.51%、14.94%、18.91%,潮土依次为8.49%、9.71%、11.34%、16.2%;旱地土壤各处理耐分解氮组分的矿化贡献率之间无显著差异,黑土为86.24%(83.96%—88.51%),潮土为88.46%(86.71%—90.20%)。【结论】旱地易分解氮组分净氮矿化潜势和矿化贡献率对不同施肥措施的反应较耐分解氮组分敏感,各施肥处理易分解氮组分净氮矿化潜势显著高于耐分解组分,NPKM处理两组分矿化潜势差异最大,且对氮素矿化潜势和矿化贡献率的提高优于NPKS处理,更优于NPK处理。

【Objective】Labile nitrogen（Lab-N） and recalcitrant nitrogen（Rec-N） are important components of soil organic matter, and their mineralization ability has an effect on organic nitrogen turnover properties. The objective of this study is to research the mineralization characteristics of soil labile and recalcitrant nitrogen under different long-term fertilization, and to provide a basis for different fertilization measures and their nitrogen supplying capacities. 【Method】Using laboratory incubation method, soil labile and recalcitrant nitrogen fractions separated by particle size-density separation method were studied under four treatments, namely no fertilizer（CK）, chemical fertilizer（NPK）, chemical fertilizer combined with straw（NPKS）, and chemical fertilizer combined with manure（NPKM） from two typical long-term experiment sites（black soil and fluvo-aquic soil） in China. 【Result】Results of laboratory sieving and incubation showed that the method was simple and suitable to study the mineralization characteristics of soil labile and recalcitrant nitrogen fractions in which average soil mass recovery and average soil nitrogen recovery were both above 97%, and average mineralization contribution rate（soil labile and recalcitrant nitrogen fractions mineralization amount to that oforiginal soil） was 99.91%（99.89%-99.93%）. Net-nitrogen（Net-N） mineralization potential of soil labile nitrogen under treatments of NPK, NPKS and NPKM were higher than that under CK treatments by 26.82%-137.10%（except NPK of black soil）. Different fertilizer treatments had a significant influence on Net-N mineralization potential of soil labile nitrogen in black soil and fluvo-aquic soil. The Net-N mineralization potential of soil labile nitrogen in black soil under NPKM treatment was 1.48 mg·kg-1·d-1, which was higher compared with NPKS（1.02 mg·kg-1·d-1） and NPK（0.75 mg·kg-1·d-1）. The Net-N mineralization potential of soil labile nitrogen in fluvo-aquic soil under NPKM treatment was 1.17 mg·kg-1·d-1, which was higher compared with NPKS（0.89 mg·kg-1·d-1） and NPK（0.76 mg·kg-1·d-1）. The Net-N mineralization potential of soil recalcitrant nitrogen had no significant difference among different fertilizer treatments. The average mineralization potential was 0.58 mg·kg-1·d-1（0.52-0.63 mg·kg-1·d-1） in black soil and 0.51 mg·kg-1·d-1（0.40-0.62 mg·kg-1·d-1） in fluvo-aquic soil. The Net-N mineralization potential of soil labile nitrogen was higher than that of soil recalcitrant nitrogen in both black soil and fluvo-aquic soil, and it showed the biggest difference under the NPKM treatment. Among them, the Net-N mineralization potential of soil labile nitrogen was 1.41, 1.39, 1.75, and 2.35 times that of soil recalcitrant nitrogen as the order of CK, NPK, NPKS, and NPKM in black soil, and was 1.22, 1.33, 1.56, and 1.87 times as the same order in fluvo-aquic soil. The mineralization contribution rate of soil labile nitrogen was influenced by different fertilizer measures in this order CK, NPKNPKSNPKM. The rate of black soil was 10.82%, 12.51%, 14.94%, 18.91%, and the rate of fluvo-aquic soil was 8.49%, 9.71%, 11.34%, 16.2%, in which the rate under NPKM was significantly higher than the other treatments. There were no significant differences among the mineralization contribution rate of upland recalcitrant nitrogen under different fertilizer treatments. The average mineralization contribution rates were 86.24%（83.96%-88.51%） in black soil and 88.46%（86.71%-90.20%） in fluvo-aquic soil. 【Conclusion】 The Net-N mineralization potential and mineralization contribution rates of upland soil labile nitrogen were more sensitive to different fertilizer measures than that in upland soil recalcitrant nitrogen. Under different fertilization measures, the Net-N mineralization potential of soil labile nitrogen was significantly higher than that of soil recalcitrant nitrogen, especially for the treatment of NPKM. Long-term application of NPKS or NPKM will improve Net-N mineralization potential and mineralization contribution rate of upland soil. The improvement effect is in the order of NPKMNPKSNPK.