种植绿肥与稻秸协同还田对单季稻田土壤有机碳库和酶活性的影响

种植绿肥和秸秆还田是稻田土壤培肥的重要措施。研究江汉平原单季稻田冬闲期种植绿肥及稻秸不同利用模式对土壤有机碳库和土壤酶活性的影响,为合理利用秸秆和土地资源提供科学依据。该研究基于3 a田间定位试验,以稻秸不还田不种绿肥(CK1)和不施肥空白(CK0)为对照,分析了冬闲期稻秸全量覆盖单独还田(RSM)、稻秸原位焚烧还田(RSB)、单种绿肥(GM)以及稻秸全量覆盖与种植绿肥协同还田利用(RSM+GM)等处理模式下土壤有机碳各组分含量、碳库管理指数、酶活性的变化及其与水稻产量的关系。结果表明:与CK1和CK0相比,RSB处理3 a后显著降低了土壤稳态有机碳含量,对土壤总有机碳、活性有机碳含量以及碳库管理指数均无显著影响;而GM、RSM及RSM+GM处理3a后显著提高了土壤活性有机碳含量、碳库指数、碳库活度、碳库活度指数和碳库管理指数,尤其是RSM和RSM+GM处理还可显著提高土壤总有机碳含量,且多数指标均以RSM+GM处理增幅为最大,其次是RSM处理。与CK1相比,RSB处理3a后显著提高了过氧化氢酶和蔗糖酶活性,但对土壤脲酶活性无显著影响;而RSM、GM及RSM+GM处理模式3 a后均可显著增加土壤过氧化氢酶、脲酶和蔗糖酶活性,其中RSM+GM处理模式在1 a后即可显著提高土壤脲酶活性,2 a后显著提高土壤过氧化氢酶和蔗糖酶活性,3 a后土壤过氧化氢酶和蔗糖酶活性增幅均是最大。相比于CK1,RSM和RSB处理模式3 a的稻谷增产效果均不显著,而GM和RSM+GM处理模式连续3 a显著提高了稻谷产量,增幅分别为6.88%～11.67%和6.00%～13.40%。相关性分析表明,土壤总有机碳、活性有机碳、碳库管理指数、土壤酶活性与水稻产量之间均呈极显著正相关关系。综上,在江汉平原单季稻作条件下,冬闲期稻秸全量覆盖还田或种植绿肥均可改善土壤肥力,增加作物产量,但前者更有助于土壤有机碳积累,后者更利于作物产量提升。为了兼顾秸秆资源利用、土壤质量改善和作物增产稳产,稻田冬闲期稻秸全量覆盖与种植绿肥协同还田利用模式是一种较好的选择。

Effects of co-incorporation of green manure planting and rice straw on soil organic carbon pool and soil enzyme activity in a mono-rice cropping system

Abstract: Green manure application and rice straw returning are two effective ways of improving soil fertility of paddy fields in South China. The study on the effects of straw management practices on soil fertility during the winter fallow season is of great significance for providing a scientific basis for the rational utilization of straw and land resources in the rice cropping system of South China. Recently, the technique for co-application of green manure and returned rice straw has been developed though little is known about the soil carbon pool and soil enzyme activity under co-application of the two organic materials in a mono-rice cropping system. This study is based on a three-year field experiment conducted during the winter fallow seasons from September 2010 to September 2013 in Jianghan Plain, Central China. The aim was to examine the effects of different treatments on soil organic carbon components, Carbon Pool Management Index (CPMI), soil enzyme activities and crop yield in a mono-rice cropping system were studied. The experiments included six treatments: 1) Rice Straw Mulching (RSM), 2) Rice Straw Burning(RSB) in situ, 3) Green Manure(GM) planting without rice straw return, 4) rice straw mulching with green manure planting (RSM+GM), and 5) a control (CK1) with no rice straw returning and 6) a control (CK0) with no rice straw returning and chemical fertilizer application. Soil samples (at depths of 0-20 cm) were taken and analyzed after rice was harvested in each of the years. The results showed that as compared with CK0 and CK1, RSB decreased the soil Stable Organic Carbon (SOC) content significantly (P<0.05) only in 2013. Conversely, the other treatments, RSM, GM and RSM+GM increased soil Active Organic Carbon(AOC) content, Carbon Pool Index(CPI), Activity (A), Activity Index (AI) and CPMI significantly (P<0.05). Additionally, the treatments of RSM and RSM+GM alsoincreased soil total organic carbon (TOC) content significantly (P<0.05). Most of these indices showed the largest increase in RSM+GM treatment, followed by RSM treatment, which was significantly higher than GM treatment. Compared with CK0 and CK1, RSM, GM and RSM+GM treatments also increased soil catalase, urease and invertase activities. The RSM+GM treatment significantly (P<0.05) increased soil urease activity in 2011, 2012 and 2013, and improved soil catalase and invertase activity in 2012 and 2013, and proved to be superior to other treatments. Compared with CK1, the grain yields of rice in GM and RSM+GM treatments were significantly (P<0.05) increased by 6.88%-11.77% and 6.00%-13.40%, respectively, across the three years. However, no significant difference was observed among the grain yields by RSM, RSB and CK1 treatments. Pearson''s correlation analysis indicated that rice yield was significantly (P<0.01) positively correlated with TOC, AOC, CMPI and soil catalase, urease and invertase activities. These results indicated that the co-application of returned rice straw and green manure in winter fallow season could improve soil fertility and increase crop yield, but the former was more conducive to the accumulation of soil organic carbon pool, while the latter was more conducive to the improvement of crop yield. For better soil quality, higher crop yield and the efficient utilization of crop straw, the co-incorporation of rice straw and green manure was recommended for the mono-rice cropping system in ecological condition similar to those in the location of this study..