长期定位试验条件下红壤性水稻土有机质的变化

Changes of Organic Matter in Paddy Soil Derived from Red Soil in a Long-term Lo cated Experiment

通过22年长期定位试验,研究了红壤性水稻土有机质的含量及其结合形态在3种稻作制、3种有机肥施用水平及2种地下水位深度条件下的长期演变规律,结果表明:红壤旱土改水田后,土壤有机质含量逐渐增加,各处理平均增长15.2gkg-1,增长率达98.9%。不同稻作制间,以稻—稻—冬泡处理土壤有机质增长幅度最大,21年共增加了18.0gkg-1,增长率达116.9%;稻—稻—冬绿处理次之,共分别增长15.8gkg-1和102.6%;稻—稻—冬油处理最低,仅分别增长11.9g kg-1和77.3%。不同有机肥施用水平间,以高量有机肥处理土壤有机质增长最快,21年共增加了17.9gkg-1,增长率为116.2%;常量有机肥处理次之,共分别增加16.1gkg-1和104.5%;化肥处理最低,共分别增加11.8gkg-1和76.6%。不同地下水位深度对土壤有机质积累的影响不显著。土壤腐殖质结合形态以紧结态为主,占腐殖质总量的50～70%,松结态腐殖质次之,占20～40%,稳结态腐殖质最少,仅5～11%。冬种处理土壤腐殖质的松/紧比大于冬泡处理。施用有机肥料能提高土壤腐殖质的松/紧比。

A long-term field experiment was carr ie d out to study the changes of organic matter (O.M.) and combined forms of humus in paddy soil derived from red soil under 3 rice-based cropping systems, 3 apply ing rates of green manure and 2 ground-water levels. The results showed the cont ent of organic matter was increased gradually when upland soil was puddle and cr opped under submerged conditions. Among the different rice-based cropping system s, the increase rate of O. M. in the treatment of rice-rice-flooded fallow in winter was the highest, that in the treatment of rice-rice-astragalus came the s econd, and that in the treatment of rice-rice-rape was the lowest. Among the dif ferent application rates of green manure, the increase rate of O.M. in the trea tment of high application rate of green manure was the highest, that in the trea tment of normal application rate of green manure came the second, and that in th e treatment of chemical fertilizer was the lowest. The effects of groundwater le vels on changes of O. M. were not significant. The tightly bonded humus (TH) was the main combined form of humus. The loosely bonded humus (LH) was the second, and the stably bonded humus was the least. The values of LH/TH in those treatme nts of rice-rice-astragalus or rape in winter were higher than that of the treat ment of rice-rice-flooded fallow in winter. Manuring could increase the LH/TH of humus.