冬季不同种植模式对稻田土壤团聚体及其有机碳的影响

为探究冬季不同种植模式对稻田土壤结构和质量的影响,设置5种冬季种植模式:冬季休闲(冬闲)、冬种紫云英、冬种油菜、冬种大蒜和冬季轮作(马铃薯、紫云英、油菜),通过测定稻田不同土层土壤团聚体组成和团聚体有机碳含量,分析稻田土壤团聚体的水稳性和团聚体有机碳分布。结果表明,在0~30 cm土层深度:>2 mm粒级的土壤团聚体含量最高,其次是<0.053 mm粒级的土壤团聚体,1~2、0.5~1、0.25~0.05、0.053~0.25 mm粒级的土壤团聚体含量相近;各冬季种植处理模式均提高了稻田水稳性团聚体的平均质量直径(MWD)和平均几何直径(GMD),其中冬种油菜、冬季轮作以及冬种紫云英处理的MWD较冬闲处理分别显著提高21.50%、21.16%、16.32%(P<0.05),冬种油菜和冬季轮作处理的GMD较冬闲处理分别显著提高83.31%、62.50%(P<0.05);冬季不同种植模式显著降低了土壤水稳性团聚体的分形维数(P<0.05),有利于维持土壤结构的稳定性;相对于冬闲处理,其余不同冬季种植模式处理的各粒径下土壤团聚体有机碳含量有增加的趋势。综上可知,冬季不同种植模式均有利于稻田土壤团聚体稳定性的提高和各粒级下团聚体有机碳的积累,其中冬季轮作模式的效果最佳。本研究结果为南方冬闲田优化种植模式提供了理论依据。

Effects of Winter Different Planting Patterns on Soil Aggregates and Organic Carbon in Paddy Fields

In order to explore effect of different winter planting patterns on soil structure and quality of paddy fields, five winter planting modes were set in the experiment, including winter fallow, winter Chinese vetch, and winter rape, winter garlic and winter rotation (potato, Chinese vetch and rape). The water stability and distribution of aggregates in paddy fields were analyzed by measuring the composition of soil aggregates and the organic carbon content of aggregates in different layers of paddy fields. The results showed that the soil aggregate content(> 2mm) was dominant (the highest), followed by <0.053mm, while the soil aggregate content of 1~2mm, 0.5~1mm, 0.25~0.05mm, 0.053~0.25 mm was similar; the mean weight diameter (MWD) and geometric mean diameter (GMD) of water-stable aggregates in paddy fields were increased by all winter cultivation treatments. The MWD of winter rape treatment, winter potato, Chinese milk vetch and rape rotation treatment and winter Chinese milk vetch treatment were increased by 21.50%, 21.16% and 16.32% respectively (P<0.05). GMD of potato, Chinese milk vetch and rape in winter rotation treatment increased by 44.74% and 62.50%, respectively, compared with that in winter fallow treatment (P<0.05); in addition, the fractal dimension values of soil water-stable aggregates were significantly reduced by different winter planting patterns (P<0.05), which was beneficial to the stability of soil structure; the organic carbon content of soil aggregates increased with different winter planting patterns. Therefore, different winter planting patterns are beneficial to enhance the paddy soil aggregate stability and the accumulation of organic carbon with different particle fraction of soil water-stable aggregates. The winter crop rotation with potato milk vetch and rape showed the best result. The findings provide a theoretical basis for the selection of the optimal pattern of winter fallow fields in southern China.