Effects of Long-Term Fertilization on the Distribution of Carbon, Nitrogen and Phosphorus in Water-Stable Aggregates in Paddy Soil

We investigated the size distribution of water-stable aggregates and the soil carbon, nitrogen and phosphorus concentration over aggregate size fractions based on a long-term （1990-2006） fertilization experiment in a reddish paddy soil. The results showed that the largest water-stable aggregate （WSA） （〉5 mm） and the smallest WSA （〈0.25 mm） took up the first largest proportion （38.3%） and the second largest proportion （23.3%）, respectively. Application of organic materials increased the proportion of the large WSA （〉2 mm） and decreased the proportion of the small WSA （〈1 ram）, resulting in an increase in the mean weight diameter of WSA, whereas application of chemical fertilizer had little effect. Application of organic materials, especially combined with chemical fertilizers, increased total carbon, nitrogen and phosphorus concentrations in all sizes of WSA, and total carbon, nitrogen and phosphorus were prone to concentrate in the large WSA. Further more, application of organic materials improved the supply effectiveness of available phosphorus, whereas had little influence on the labile carbon in WSA. Application of chemical fertilizers improved concentrations of total and available phosphorus in all sizes of WSA, whereas had little influence on total carbon and nitrogen contents. Economical fertilization model maintained the soil fertility when compared with full dose of chemical fertilizers, indicating that using organic materials could reduce chemical fertilizers by about one third.

长期不同施肥措施下黄泥田水稻土团聚体组成、稳定性及养分分布特征

为了找出适合低肥力黄泥田的培肥模式,以单施化肥(NPK)处理为对照,研究长期(8 a)不同培肥措施[化肥配施秸秆同时添加秸秆快腐菌剂(NPK+RS)、控释BB肥配施牛粪(BBF+CM)]下黄泥田水稻土团聚体组成、稳定性及养分分布特征。结果表明,与试验开始时土壤养分状况相比,3种施肥处理总体上均提高了耕层土壤有机质、全氮、有效磷含量,其中,BBF+CM处理有机质、全氮、有效磷含量分别显著提高了41%、49%、55%,提升效果最明显。与NPK处理相比,NPK+RS和BBF+CM处理提高了>2.00 mm粒径团聚体所占比例及平均质量直径(MWD)、几何平均直径(GMD),提升幅度BBF+CM处理稍高于NPK+RS处理。3个施肥处理水稻根际土壤团聚体MWD和GMD均随着水稻生育时期的推进逐渐增大,而非根际土壤团聚体MWD和GMD总体上在水稻分蘖期最大、拔节期最小。在水稻分蘖期,3个施肥处理非根际土壤团聚体MWD和GMD大于根际土壤,在水稻拔节期和成熟期,结果反之。方差分析结果表明,水稻取样时间、施肥处理及其互作是影响黄泥田水稻土团聚体稳定性的主要因子。相关性分析结果表明,土壤团聚体稳定性与土壤有机质、速效钾含量分别具有极显著正、负相关关系。不同粒径团聚体养分分布存在差异,其中>2.00 mm粒径团聚体有机质和全氮含量较高,而<0.25 mm和0.25~2.00 mm团聚体有效磷、速效钾含量较高。与NPK处理相比,NPK+RS和BBF+CM处理总体上均可以显著提高各级粒径团聚体有机质、全氮、有效磷、速效钾含量,其中,NPK+RS处理各粒径团聚体有机质含量提高19%~23%,全氮含量提高19%~29%,有效磷含量提高26%~49%,速效钾含量提高131%~157%;而BBF+CM处理各粒径团聚体有机质含量提高23%~34%,全氮含量提高28%~81%,有效磷含量提高47%~178%,速效钾含量提高17%~41%。综上所述,BBF+CM和NPK+RS 2种施肥模式均能提升黄泥田土壤养分含量、改善土壤结构,其中BBF+CM处理效果较优,可以作为低产黄泥田土壤生产力提升的有效措施。