The influence of long-term fertilization on microbial biomass nitrogen and organic nitrogen fractions in paddy soil

chinois. 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。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。不施肥处理（对照）土壤的MBN含量分别为30 mgand#8226;kg-1（新化）和28 mgand#8226;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 mgand#8226;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。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。

anglais. Organic N is the most important N form in soil. Soil microbial biomass nitrogen (MBN) is considered as a sensitive indicator of soil quality and fertility. The influence of long-term fertilization on MBN and acid hydrolysable organic nitrogen (AHON) fractions in paddy soil were studied. Soil samples were collected from the plough layer in two long-term fertilization experiments done in Hunan province. Soil MBN was measured by the fumigation-extraction method, and soil organic N was fractionated by acid hydrolysis-distillation method. MBN in CK at XH, TJ sites were 30 mgand#8226;kg-1, 28 mgand#8226;kg-1, respectively. Compared to CK, application of NPK showed no significant effect on soil MBN. However, NPK plus manure or straw could significantly increase the content of MBN. AHON accounted for 69%-89% of the soil total N and the fractions of AHON varied in different treatments. AHON in CK treatments at XH, TJ sites were 821.54 mgand#8226;kg-1, 1 471.35mgand#8226;kg-1, respectively. Compared to CK, application of NPK plus manure or straw greatly increased the contents of AHON, amino acid N (AAN), amino sugar N (ASN), and ammonia N (AN). The contents of unidentified hydrolysable N (HUN) decreased in different treatments, while non-hydrolysable N (NHN) increased in all treatments. The results showed a very significant positive correlation between MBN and AHON. Soil MBN was closely related to soil AAN and ASN content, respectively. Long-term fertilization help to maintain soil N contents in plough layer of the paddy soils. Based on the results mentioned above, the conclusion is that application of chemical fertilizers plus manure or straw is an effective way for maintaining the quantity and quality of soil organic N and the amount of the microbial biomass in paddy soils.