长期施肥对黄泥田碳和氮及氮素利用的影响

 【目的】研究长期施肥下南方黄泥田碳和氮的变异规律及其与硝态氮累积的关系，阐明影响硝态氮累积的主要因素。【方法】以25年定位试验为平台，通过室内分析和统计分析，研究不施肥、施化肥和有机无机肥配施处理条件下黄泥田有机碳（SOC）、全氮（TN）、微生物量碳、微生物量氮和氮素利用率的变化及与硝态氮累积的相关关系。【结果】（1）双季稻区，在提高土壤SOC、TN、碱解氮、微生物量碳和微生物量氮含量方面，有机无机肥配施明显优于单施无机肥，并以配施高量（70%）或低量有机肥（30%）效果最佳。（2）在等养分量条件下，与施无机肥处理相比，配施高量或低量有机肥处理在土壤硝态氮含量和累积量均有显著增加，有机无机肥等比例配施处理的硝态氮含量和累积量有大幅减少，与不施肥处理基本相当。【结论】提高土壤质量以配施高量有机肥效果最好，降低土壤中硝态氮累积量以等比例配施有机无机肥效果最佳。因此，从提高土壤质量和保护生态环境方面考虑，该区域有机无机肥配施应注意配施比例。影响硝态氮累积的因素主要有土壤有机碳、全氮、微生物量碳和微生物量氮，其中最直接的影响因素是土壤微生物量碳。

Effects of Long-term Fertilization on Carbon and Nitrogen in Yellow Clayey Soil and Its Nitrogen Utilization

【Objective】Under the same nitrogen application condition, the variation of carbon and nitrogen in yellow clayey soil and its relationship with NO3--N accumulation under long-term fertilization were studied to illustrate the main factors affecting the NO3--N accumulation. 【Method】The changes of soil organic carbon(SOC), total nitrogen(TN), microbial biomass carbon(SMBC), microbial biomass nitrogen(SMBN), recovery efficiency of nitrogen and the correlation among accumulated amount of NO3--N in a yellow clayey soil after fertilization were analyzed based on a 25 year long - term fertilizer experiment in yellow clayey soil in Nanchang County, Nanchang, China. In an experiment carried out in 1984 at this site, 8 different treatments were designed in an early rice-late rice rotation system. The treatments were no fertilizer(CK), nitrogen fertilizers deficiency (PK)，potassium fertilizers deficiency (NP), phosphorus fertilizers deficiency (NK), balanced chemical fertilizers application (NPK), 70% chemical fertilizers substituted by 30% organic manure in balanced chemical fertilizers application (70F+30M), 50% chemical fertilizers substituted by 50% organic manure in balanced chemical fertilizers application (50F+50M), 30% chemical fertilizers substituted by 70% organic manure in balanced chemical fertilizers application (70F+30M).【Result】Two main results were found from this experiment. First, in the double rice-cropping syetem areas, combined application of organic manure and chemical fertilizers were better than inorganic fertilizers for improving the SOC, TN, available N, SMBC and SMBN, in which combined application of high amount (70%) or low amount (30%) of organic manure was the best. Second, the content and accumulated amount of NO3--N of the combined high amount or low amount of organic fertilizer treatments were more than chemical fertilizers in the soil profile under the same nitrogen condition. The content and accumulated amount of NO3--N of the same ratio of organic manurecombined with chemical fertilizers treatments which greatly reduced the accumulated amount of NO3--N in the soil were equal with no fertilization. 【Conclusion】High amount and the same ratio of organic manure combined with chemical fertilizers is the best to improve soil quality and decrease the accumulated amount of NO3--N in soil, respectively. In consideration of soil quality and environmental protection, the ratio of organic manure combined with chemical fertilizers should be used in the region. Factors affecting NO3--N accumulation are SOC, TN, SMBC and SMBN under the same nitrogen conditions, and SMBC is the most important and direct factor.