粮田改种蔬菜对水稻土土壤结构与有机质含量的影响

利用江苏省江都市马凌村良种场多年粮田（对照）和粮田改种蔬菜20年以上田块,研究粮改蔬对0～60 cm土层团聚体、土壤容重、孔隙度、固液气三相比和有机质含量与分配的影响。结果表明,与对照相比,长期蔬菜种植减少了0～20 cm土层中0.250～1.000 mm和0.053～0.250 mm粒径团聚体的数量,却增加了〈0.053 mm微团聚体的数量;增加了20～60 cm土层中0.053～0.250 mm小团聚体的数量,降低了〈0.053 mm微团聚体的数量。长期蔬菜种植使0～20 cm耕层土壤容重显著降低21.0%、气孔度显著增加29.6%,20～40 cm土层气孔度显著降低了42.3%,固、液相所占比例在0～20 cm土层降低但在20～40 cm土层增加。两种利用方式下,0～20 cm土层中有机质含量分别占0～60 cm土层有机质含量的58.9%和63.3%,长期蔬菜种植下0～20 cm耕层土壤有机质含量显著降低了20.8%。粮改蔬多年耕种可改善土壤的物理结构却减少了耕层土壤有机碳固储数量。

Effects of Converting Cropland into Vegetable field on Soil Structure and Organic Matter Content in Paddy Soil

With representative paddy field（ control） and vegetable field converted from cropland for over 20 years in Maling farmland,located in Jiangdu City,Jiangsu Province as materials,the effects of planting vegetable instead of crop on soil aggregate,bulk density,porosity,proportion of solid,liquid and gas,and content and distribution of soil organic matter（ SOM） in 0 ～ 60 cm soil layer were investigated. The results showed that compared with control,long-term vegetable planting decreased the amounts of 0. 250 ～ 1. 000mm and 0. 053 ～ 0. 250 mm aggregates in 0 ～ 20 cm soil layer and increased the amount of micro-aggregate lower than 0. 053 mm,while increased the amount of 0. 053 ～ 0. 250 mm aggregate and decreased the amount of micro-aggregate lower than 0. 053 mm in 20 ～ 60 cm soil layer. Long-term vegetable planting significantly decreased soil bulk density by 21. 0% and significantly increased soil porosity by 29. 6% in 0 ～ 20 cm soil layer; the soil porosity in 20 ～ 40 cm soil layer was significantly decreased by 42. 3%; the proportions of solid and liquid in 0 ～ 20 cm soil layer decreased,while those in 20 ～ 40 cm soil layer increased. The ratio of SOM content in 0 ～ 20 cm soil layer to that in 0 ～ 60 cm soil layer was 58. 9% and 63. 3% respectively under two land use patterns. Long-term vegetable planting significantly decreased 0 ～ 20 cm topsoil SOM content by20. 8%. Long-term planting vegetable instead of crop could improve soil physical structure but decrease SOM content in topsoil.