长期施肥对水稻土耕层微生物生物量氮和有机氮组分的影响

Effects of Long-Term Application of Fertilizers on Soil Microbial Biomass Nitrogen and Organic Nitrogen Components in Subtropical Paddy Soils

以亚热带2个国家级稻田土壤肥力变化长期定位监测点的土样为对象,研究了长期施肥对土壤微生物生物量氮(BN)和有机氮组分的影响.采用氯仿熏蒸-K2SO4提取法和酸水解-蒸馏法分别对耕层土壤微生物生物量氮和有机氮组分进行了测定.结果表明,经过17a的有机无机肥配合施用,土壤氮含量水平较低的宁乡点,土壤全氮平均每年增加约40 mg.kg-1,而土壤氮含量水平较高的南县点,平均每年增加约55 mg.kg-1.有机无机肥长期配合施用也提高了土壤微生物生物量氮和微生物生物量氮占全氮的比例;同时也显著增加酸解性氮及氨基酸态氮、酸解未知氮的含量.此外,土壤酸解性氮及其组分均与微生物生物量氮存在极显著的正相关关系,其中氨基酸态氮和酸解未知氮对微生物生物量氮的影响最大.研究表明,有机无机肥配施是使稻田土壤氮素含量提高的重要措施,有机无机肥配施促进了土壤氮库的积累,即易矿化和较难矿化2部分氮库同时增加.

The effect of long-term fertilization on soil organic nitrogen components and microbial biomass nitrogen （BN） in paddy soils from two experiment sites in Hunan province were studied. Soil samples were collected from the plough layers of different fertilizer treatments. Soil BN was measured by the fumigation-extraction method, and soil organic N was fractionated by acid hydrolysis-distillation method according to the scheme of Bremner （1965）. Results showed that the soll N increased 40 mg·kg^-1 every year at Ningxiang site （low N level） for 17 years under the application combined of fertilizers and manure , while that at Nanxian site （ high N level） was 55 mg· kg^- 1 . Soil total nitrogen （TN）, total hydrolysable nitrogen （THN） and microbial biomass nitrogen（ BN ） were increased by long-term combined application of chemical fertilizer and manure （ NPKM ）. NPKM significantly increased the content of TN, BN, total hydrolysable nitrogen （ THN ）, ammonia acid nitrogen （AAN）, hydrolysable unidentified nitrogen （HUN） and the percentage of BN to TN. Besides, NPKM increased the easily mineralizable BN, AAN, and low decomposed HUN. There was positive correlated relationship between BN and THN and different THN components, and the effect of AAN and HUN on BN was biggest. It is obvious that NPKM increased soil fertility and enhanc the nitrogen- supplying capability of paddy soils. NPKM had the effect on increasing soil nitrogen capability of paddy soils, both easily decomposed fractions and difficultly decomposed ones.