长期施肥对两种稻田土壤微生物量氮及有机氮组分的影响

【目的】土壤有机氮和微生物量氮（MBN）是土壤肥力的重要指标，并对土壤质量演变具有重要的指示意义。本文旨在研究长期不同施肥处理对稻田土壤MBN和酸解有机氮（AHON）及其组分的影响。【方法】以湖南省新化县和桃江县两个稻田肥力长期定位试验点的土样作为研究对象，采用氯仿熏蒸-K2SO4提取法和酸解-蒸馏法分别对土壤的MBN及AHON进行了测定。【结果】不施肥处理（对照）土壤的MBN含量分别为30 mg•kg-1（新化）和28 mg•kg-1（桃江）。与对照相比，单施化肥对土壤MBN含量没有显著的影响，而化肥配施有机肥则显著提高了土壤MBN的含量。AHON占土壤全氮的69%～89%，是土壤氮的主体。长期不同施肥处理对AHON含量及其组分有显著的影响。对照处理的土壤AHON含量在新化和桃江两试验点分别为821.54和1 471.35 mg•kg-1。化肥配施有机肥可以提高土壤AHON及其组分中的氨基酸氮（AAN）、氨基糖氮（ASN）和氨态氮（AN）的含量。与对照处理相比，不同施肥处理使土壤酸解未知氮（HUN）的含量有所降低，而使非酸解性氮（NHN）的含量有所增加。土壤TN与MBN和AHON之间的相关性均达极显著水平，土壤MBN与AHON和氨基态氮之间存在显著的正相关关系。【结论】土壤氮素含量的提高和演变与施肥措施密切相关，化肥配合有机肥施用能提高土壤有机氮及微生物量氮的含量，增加了与土壤微生物密切相关的氨基态氮含量。

The Influence of Long-Term Fertilization on Microbial Biomass Nitrogen and Organic Nitrogen Fractions in Paddy Soil

Soil samples from two long-term fertilization experiments carried out on the paddy soil in subtropical area of China for 17 years were measured. The soil samples were collected from the plough layers of different fertilizer treatments. Soil organic nitrogen fractions and microbial biomass nitrogen were studied. Results showed that long-term fertilization increased the soil organic nitrogen fractions in topsoil of paddy soil. The application of chemical fertilizers combined manure or straw could significantly increased the content of soil total N、available N、microbial biomass N and acid hydrolysable N, but had no apparent effects on non-hydrolysable N. The content of the different fractions of acid hydrolysable N varied with different treatments. Compared with the check, application of manure or straw with chemical fertilizers greatly increased the contents of amino acid N, ammonium N, amino sugar N while the contents of hydrolysable unidentified nitrogen (HUN) were decreased after long-term fertilization. Of the total N in the soils studied 69%-89% was acid hydrolysable N. The results showed a very significant positive correlation between microbial biomass N and acid hydrolysable N after fertilizer application. The soil microbial biomass N was also closely related with the amino acid N, amino sugar N and ammonium N. There was no significant correlation of microbial biomass N with HUN. It was concluded that application of organic manures along with chemical fertilizers is an effective way of maintaining the quantity and quality of soil organic N and the size of the microbial biomass. The traditional use of manures should therefore be promoted in order to maintain long-term soil productivity even where chemical fertilizers are being used to achieve high yields.