长期不同施肥对黄泥土水稳性团聚体颗粒态有机碳的影响

Effect of Different Long-term Fertilization Treatments on Particulate Organic Carbon in Water-stable Aggregates of a Paddy Soil

研究了长期不同施肥处理（化肥与秸秆配施、化肥与猪粪配施、单施化肥和不施肥）下太湖地区黄泥土耕层水稳性团聚体颗粒态有机碳含量的变化。结果表明，供试土壤水稳性团聚体组成以〉2mm和2—0．25mm粒径为主，施肥下〉2mm水稳性团聚体显著增加，并伴随2—0．25mm水稳性团聚体明显减少。颗粒态有机碳主要存在于〉2mm水稳性大团聚体中，并随着水稳性团聚体粒径的减小而明显减少。〉2mm水稳性大团聚体中的POE对施肥的响应较为敏感，以化肥与秸秆配施下该粒径水稳性团聚体中POE的积累效果最为明显。而化肥与猪粪配施则显著增加了2-0．25mm和0．25-0．053mm水稳性团聚体中的POC含量。土壤不同层次水稳性团聚体中POE的来源不同，在0—5cm表层可能主要来源于作物根茬生物量，而在5—15cm土层则可能跟施入的外源有机物有关。

Particulate organic carbon （POC） in soils is generally considered as a labile pool involved in formation and turnover of water- stable aggregates, which is active in response to environmental and management changes. In this paper, variation of POC in water - stable aggregates was studied in a paddy soil under a long - term fertilizer application trial. The treatments included chemical fertilizer with straw return, fertilizer alone and no fertilizer application. The water stable aggregates chemical fertilizer plus pig were separated by wet sieving matter from these aggregates were further segregated by rotary shaking followed by sieving. The manure, chemical and the particulate POC content was determined by a CNS Analyzer. The water - stable aggregates were dominated by the size fraction of 〉 2mm and 2 - 0.25mm in the paddy soil. However, the size fraction of 〉2ram was increased and that of 2 -0. 25mm decreased under the fertilization treatments compared to that under no fertilization. POC was found to accumulate in water - stable aggregates larger than 2mm in size and to decrease sharply with the decreasing size. Furthermore, POC in 〉 2mm water -stable aggregates was significantly higher under chemical 0. 25mm and 0.25 -0. 053mm in size slightly higher under fertilization plus straw return, while POC in those of 2 - chemical fertilization plus pig manure, indicating a higher sensitivity of POC in larger aggregates to fertilization practices. Regression coefficients showed a possible source of POC in water - stable aggregates from increased crop biomass in topsoil （0 -5cm） and organic matter applied in sub - surface layer （5 - 15cm）.