稻草易地还土对丘陵红壤团聚体碳氮分布的影响

Effects of Ex Situ Incorporation of Straw on Distributions of C and N in Aggregates of Hilly Red Soils

利用新垦坡地、熟化旱地两个定位试验的典型处理（不施肥、化肥、稻草＋NP），研究稻草易地还土对丘陵红壤水稳定性大团聚体（〉0．25mm）内碳、氮分布的影响。结果表明，稻草易地还土提高了土壤大团聚体含量；团聚体粒径越大，有机碳和全氮的含量越高；与对照相比，稻草易地还土提高大团聚体内的有机碳含量10．1％～78．5％、全氮含量9．4％～63．6％（P〈0．05），同时也显著提高二者在较大粒径（1～2mm，2～5mm）团聚体内的分配比例；与化肥处理相比，稻草易地还土提高〉0．5mm各粒级大团聚体内的有机碳含量6．5％～46．1％，也提高了0．5～1mm，1～2mm，2～5mm团聚体内的全氮含量8．7％～16．1％（P〈0．05）。水稳定性大团聚体对土壤碳、氮具有强富集和物理保护作用；稻草易地还土提高水稳定性大团聚体内碳、氮的含量和分配比例，是改良丘陵红壤结构、提高并协调土壤肥力的有效保育措施。

Two experiments in newly-culltivated slope land and upland with three treatments, Nil （CK）, NPK （NPK）, Strawq-NP （SNP）, were selected to analyze the effects of ex situ rice straw incorporation on the distribution of organic carbon and nitrogen in water-stable macro-aggregates of hilly red soils. Results showed that, ex situ incorporation of straw increased water-stable macro-aggregates and the concentrations of organic carbon and nitrogen increased with increase of water-stable aggregate-size; ex situ incorporation of straw significantly increased the concentrations of organic carbon and nitrogen in water-stable macro-aggregates by 10. 1%- 78.5% and 9.4%-63.6% （p 〈0. 05）, and also increased the ratios of organic carbon and nitrogen in water-stable macro-aggregates （2- 5 mm or 1 - 2 mm） to soil; Compared to inorganic fertilizer, ex situ incorporation of straw significantly increased the concentrations of organic carbon by 6.5%-46.1% in 0.5-1 mm, 1-2 mm, 2-5 mm, -5 mm water-stable aggregates and nitrogen by 8.7%-16.1% in 0. 5-1 mm, 1-2 mm, 2-5 mm water-stable aggregates. Water-stable macro-aggregates have high potential to accumulate organic C and N, and ex situ incorporation of straw increased the concentrations and distributions of organic C and total N in water-stable macro-aggregates, which increased the ability of regulating soil fertility. Therefore, ex situ incorporation of straw was effective measure to improve soil structure, enhance and regulate soil fertility in hilly red soils.