长期双季稻绿肥轮作对水稻产量及稻田土壤有机质的影响

以中国农业科学院红壤实验站1982年布置的长期定位试验为研究对象，分析了长期双季稻绿肥轮作体系下水稻产量变化趋势、稻田土壤有机质变化特征及土壤活性有机质组成。结果表明，绿肥作物与双季稻轮作种植后，水稻产量显著高于冬闲对照，绿肥作物紫云英、油菜和黑麦草处理年平均水稻产量（1982-2008）分别为10.8 t?hm-2?a-1，10.2 t?hm-2?a-1和10.0 t?hm-2?a-1，较冬闲对照分别提高27.2%，20.5%和18.1%。试验前期（1982-1993）种植绿肥作物各处理之间水稻产量无显著差异，试验开展11年后（1994-2008）种植紫云英处理水稻产量显著高于油菜和黑麦草处理。长期双季稻绿肥轮作土壤有机质随年份显著增加，双季稻紫云英轮作土壤有机质积累速度最快，年增加0.31 g?kg-1，双季稻黑麦草次之，土壤有机质年增加0.28g?kg-1，双季稻油菜轮作土壤有机质年增加0.26g?kg-1。种植绿肥作物紫云英稻田土壤活性有机质显著高于其它处理。种植绿肥作物各处理土壤有机碳、全氮、土壤微生物量碳和土壤微生物量氮含量均显著高于冬闲对照。其中黑麦草和紫云英处理土壤微生物量碳含量及微生物熵显著高于油菜和冬闲对照处理。在湘南红壤丘陵双季稻区，种植绿肥作物对提高水稻产量、增加土壤有机质、提高土壤有机质活性具有重要意义，绿肥选择上以紫云英对水稻产量和稻田土壤培肥综合效果最好。

Effects of long-term double-rice and green manure rotation on rice yield and soil organic matter in paddy field

Rotation cropping systems have important significance to soil fertility, productivity and ecological function in paddy field. We analyzed the long-term data from a field experiment started in 1982 to investigate the effects of rotation cropping of double-rice with various green manure on the dynamics of rice yield and the total and labile soil organic matter in Red Soil Experimental Station CAAS. Four rotation cropping system were selected by three replication, which were rotation of double rice with Chinese milk vetch (Astragalus sinicus L.), rape (Astragalus sinicus L.), ryegrass (lolium multiflorum) and winter fallow. Results showed that, during the duration from 1982 to 2008, the averaged annual rice yield were 10.8 t?hm-2?a-1, 10.2 t?hm-2?a-1 and 10.0 t?hm-2?a-1 for the rotation cropping systems with Chinese milk vetch (Astragalus sinicus L.), rape (Astragalus sinicus L.) and ryegrass (lolium multiflorum) respectively. Compared with double-rice and winter-fallow cropping, rice yield was increased significantly by 27.2%, 20.5%, and 18.1% under the rotation cropping with Chinese milk vetch (Astragalus sinicus L.), rape (Astragalus sinicus L.) and ryegrass (lolium multiflorum) respectively. There was no significant difference among these rotation cropping systems with three kinds of green manure during the early period from 1982 to 1993, while the rice yield under the rotation with cultivating Chinese milk vetch was significantly higher than that under the other two kinds green manure rotations at the latter period from 1994-2008. Sustainability index of grain yield (SYI) was a reliable parameter on evaluate the productivity of sustainable cropping systems. Cultivating Chinese milk vetch could fix atmospheric nitrogen and improve soil fertility. The Sustainability index of grain yield (SYI) and potential of yield increased with cultivating Chinese milk vetch was the highest. Soil organic matter showed an increasing trend under the rotation cropping of double rice and green manure. The rotation of double rice with Chinese milk vetch had the highest annually increasing rate (0.31g?kg-1) of soil organic matter, while the rate was 0.28 g?kg-1 and 0.26 g?kg-1 for the rotation cropping with ryegrass and rape, respectively. The labile soil organic matter under the rotation with Chinese milk vetch was the highest of all the treatments. Total organic carbon, total nitrogen, soil microbial biomass carbon and nitrogen under the rotation with three kinds of green manure were significantly higher than that under the winter-fallow cropping system. Compared with rape, ryegrass has strong fibrous root system which content high organic matter and crude protein. More carbon and nitrogen were cumulated in the soil under the rotation of double rice with Chinese milk vetch and ryegrass than that under the other two cropping system. Additionally, the two rotation cropping systems of double-rice with ryegrass and Chinese milk vetch increased the microbial biomass carbon content and the ratio of microbial biomass carbon to total organic carbon (Cmic-to-Corg ) significantly compared with the cropping of double-rice and rape or fallow. In conclusion, rotation cropping of double rice with green manure had significant effects on enhancing rice yield and promoting soil organic matter quantity and quality. Rice cropping with Chinese milk rotation vetch was recommendable for rice productivity and soil fertility.