长期施肥对黄土高原旱地黑垆土水稳性团聚体的影响

通过27年的长期定位试验，研究了长期施肥对黄土高原旱地黑垆土水稳性团聚体的影响.结果表明：与自然土壤相比，黑垆土开垦后，0～10 cm和10～20 cm土层＞0.25 mm的水稳性团聚体含量分别下降了21.35%和38.82%；0.5 mm以上各粒级的水稳性团聚体含量均呈下降趋势，其中>5 mm和5～2 mm大粒径团聚体的下降幅度最大；而0.5～0.25 mm的水稳性团聚体含量却增加了104.75%和23.13%.0～10 cm土层各粒级水稳性团聚体含量均高于10～20 cm土层.单施有机肥和有机无机肥配施处理5～2 mm粒级的水稳性团聚体含量增加最多，>5 mm粒级次之；增施有机肥、有机无机肥配合施用和秸秆还田处理能显著增加大粒径水稳性团聚体含量，改善土壤团聚体的结构.各处理0～10 cm土壤水稳性团聚体平均质量直径（MMD）均大于10～20 cm土层；自然土壤的团聚体MMD显著高于同层次耕作土壤，长期施肥处理MMD大于无肥对照，有机物质培肥处理明显高于化肥处理.土壤团聚体MMD与＞0,25 mm水稳性团聚体含量呈显著正相关.

Effects of long-term fertilization on water-stable aggregates in calcic kastanozem of Loess Plateau.

The study on the size distribution of water-stable aggregates (WSAs) in calcic kastanozem of Loess Plateau after 27 years fertilization showed that compared with those of natural soil, the contents of > 0.25 mm WSAs in 0-10 cm and 10-20 cm layers of cultivated soil decreased by 21.35% and 38.82%, respectively, and those of > or = 0.5 mm WSAs also had a decreasing trend, with the greatest decrement of > 5 mm and 5-2 mm WSAs. On the contrary, the contents of 0.5-0.25 mm WSAs in the two soil layers increased by 104.75% and 23.13%, respectively. All sizes WSAs had higher contents in 0-10 cm than in 10-20 cm soil layer. Fertilization had remarkable effects on the formation of WSAs. Under the applications of organic manure and its combination with chemical fertilizers, the content of 5-2 mm WSAs increased most, followed by that of > 5 mm WSAs. After applying organic manure, organic manure plus chemical fertilizers, and straws, the contents of larger sizes WSAs increased significantly, being beneficial to the improvement of soil structure. In all fertilization treatments, the mean mass diameter (MMD) of WSAs was larger in 0-10 cm than in 10-20 cm soil layer. Compared with non-fertilization, long-term fertilization increased the MMD of WSAs, and organic manure was superior to chemical fertilizers. The MMD of WSAs was positively correlated with the amount of > 0.25 mm WSAs.