连续施用不同比例鸡粪氮对水稻土有机质积累及土壤酸化的影响

【目的】土壤酸化是自然过程。随着农业集约化发展，土壤酸化在部分农田呈加速趋势，而施肥是目前农田土壤酸化加速的重要诱因，研究有机肥和化肥对土壤酸化的作用差异及机理，对合理指导施肥及耕地保育有重要的意义。【方法】通过测定不同施肥处理的不同组分有机质含量及酸碱缓冲容量，探明不同施肥处理的酸化影响，从土壤有机质和盐基累积角度对有机-无机肥料不同比例配施条件下土壤酸化特征进行了研究。【结果】① 连续5年在等氮量（N 270 kg/hm2）且有机－无机肥料不同配施比例的处理中，水稻产量以有机肥比例为25%~50%的处理最高，其平均产量比单施化肥处理提高了5.1%，比对照提高44.9%。但处理间无显著性差异；② 土壤各活性有机质及总有机质等指标中仅总有机质含量随鸡粪施用比例的增加而持续增加，不同比例有机无机肥配合施用后，土壤的高活性有机质及低活性有机质均高于CK和纯化肥氮处理，但随着有机肥投入比例的升高，除中活性有机质和水稻产量之间呈显著的正相关外（P=0.0067**），高活性有机质、活性有机质及总有机质含量与水稻产量之间的相关性不显著（对应的概率值分别为P=0.192，P=0.208，P=0.160）；③ 施肥提高了土壤的碳库管理指数（CPMI），且其随有机肥施用比例的上升呈增加趋势。增施鸡粪提高土壤的交换性盐基离子（Ca2+、 Mg2+、 K+、 Na+）含量，导致阳离子代换量（CEC）和pH随鸡粪施用比例的提高而升高。供试土壤酸碱缓冲容量为2.07~2.36 cmol/kg，随鸡粪施用比例的上升而增加，其与土壤阳离子代换量及有机质含量呈显著正相关。表明增施鸡粪可使土壤pH及酸碱缓冲容量上升，与鸡粪使土壤盐基累积量及有机质含量的提高有关。【结论】连续有机-无机肥施用下，土壤pH上升和酸碱缓冲容量的提高可能与该试验点下盐基离子和有机质含量随鸡粪施用比例上升有关，但其最终上升幅度及平衡点尚需进一步研究。鸡粪氮替代化肥氮比例为25%~50%时，土壤性质最优，水稻产量最高。

Effect of different ratios of chicken manure N on organic matter accumulation and acidification of paddy soils

【Objectives】Soil acidification has been a major problem in the intensive agricultural systems. Irrational application of chemical and fertilizer was a major contributor to soil acidification in farmland. In this paper，the reasonable ratios of chicken manure N in the total N supply of rice production were studied through the accumulation of different labile fractions of soil organic matter and the variations of base cation contents. 【Methods】 A field experiment was successively conducted from 2003-2007, six treatments were designed: 1) No fertilizer (CK）; 2）100% organic N (M100）; 3）75% organic N（M75）; 4）50% organic N（M50）; 5）25% organic N（M25）; 6）100% chemical N（M0）. The soil samples in the fifth year were collected to determine the soil exchange cations, organic matter accumulation and soil buffering capacities. 【Results】 The rice yields are highest when 25%-50% of the total 270 kg/ha nitrogen are from organic fertilizer, with the average yield 5.1% higher than that from 100% chemical N, and 44.9% higher than that with CK, there are no significant differences between treatments with 25% and 50% organic N. The soil organic matter contents and soil carbon management index are increased with the increase of the ratio of organic fertilizer. Only the total organic matter content has positive correlation with the chick manure application ratio, and the mid-labile organic matter have positive correlation with the rice yield（P=0.0067**）. While high-labile organic matter, labile organic matter and total organic matter has no significant correlation with the rice yields (P=0.192，P=0.208，P=0.160, respectively). The increase of chicken manure application rate improves soil exchangeable base cation contents (Ca2+, Mg2+, K+ and Na+), resulting in cation exchange capacity and pH rise. The soil buffering capacity is from 2.07 to 2.36 cmol/kg and increased with the ratio of chicken manure, and there is a significant positive correlation between the cation exchange capacity and organic matter content. These results indicate that soil pH and soil buffering capacity are increased under the higher chicken manure application, and soil cations and organic matter accumulation are increased under the chicken manure application. 【Conclusions】 Continuous chicken manure application can increase soil organic matter content and labile organic matter content, significantly increase the cations exchange capacity, and a high soil buffering capacity as a concequence. The optimal substitute ratio of chicken manure N to chemical fertilizer is 25% to 50% for obtaining the satisfactory soil properties and high yield.