保护性耕作下蚕豆生育期土壤有机碳、氮含量变化与分布特征

为研究西南紫色土丘陵区坡耕地长期保护性耕作下旱作蚕豆不同生育时期农田土壤有机碳、氮相关组分分布特征,进而优化保护性耕作措施、改善土壤肥力。试验采用传统耕作、垄作、传统耕作+秸秆半量覆盖、垄作+秸秆半量覆盖、传统耕作+秸秆全量覆盖、垄作+秸秆全量覆盖6个处理。结果表明:在不同处理下,土壤总有机碳(TOC)、总氮(TN)、活性有机碳(AOC)、颗粒有机碳(POC)、水溶性氮(DN)的含量分布均表现出0～1010～20 cm土层,且随时间变化整体波动均不大。蚕豆生育期内,无秸秆覆盖条件下,垄作较平作提高了土壤总有机碳、土壤全氮、活性有机碳和颗粒有机碳的含量,但在秸秆覆盖条件下,垄作却降低了土壤总有机碳和颗粒有机碳的含量,且随着秸秆覆盖量的增加土壤颗粒有机碳和活性有机碳含量下降。同时,无论平作或垄作,秸秆覆盖较无秸秆覆盖均有利于土壤总有机碳、土壤全氮、活性有机碳和颗粒有机碳含量的提升。相关性分析表明,TOC与TN、DN、AOC之间呈显著正相关,TN与POC、DN、AOC之间呈显著正相关,POC仅表现出与DOC显著正相关,DOC与DN呈极显著正相关,DN则与AOC为极显著正相关关系。总之,单一垄作措施或秸秆覆盖能更有利于改善土壤碳、氮状况,且土壤有机碳、氮不同组分之间存在一定的耦合关系。

Changes and Distribution Characteristics of Contents of Soil Organic Carbon and Nitrogen in Broad Bean Growth Period Under Conservation Tillage

In order to optimize the conservation tillage measures and improve the soil fertility, the study of soil organic carbon and nitrogen distribution characteristics and content changes of different growth stages in broad bean growth period under long term conservation tillage in southwest China was implemented. There were six treatments including traditional tillage, ridge tillage, traditional tillage with half amount of straw mulching, ridge tillage with half amount of straw mulching, traditional tillage with full amount of straw mulching, ridge tillage with full amount of straw mulching. The results show that soil total organic carbon(TOC), total nitrogen(TN), active organic carbon(AOC), particulate organic carbon(POC), the content of water soluble nitrogen(DN) distribution decreased in the order:0-10 cm layer > 10-20 cm layer under the different treatments. And the overall fluctuations are not large over time. During the period of broad bean growth, under the conditions of no straw mulching, soil TOC, TN, AOC and POC of ridge tillage are more than traditional tillage. However, with straw mulching, ridge tillage reduced soil TOC and POC, and with the increase of straw mulch, the contents of soil AOC and POC decreased. At the same time, whether flat or ridge, straw mulching was better than no straw mulching in terms of improving soil TOC, TN, AOC and POC. Correlation analysis showed that TOC was significantly related to TN, DN, AOC; TN was significantly related to POC, DN, AOC; POC was only correlated significantly with DOC; DOC was significantly positively correlated to DN; DN was very significantly positively correlated to AOC. The results showed that single ridge tillage or straw mulching could more effectively improve the status of soil carbon and nitrogen; and there was a certain coupling relationship between the different components of soil organic carbon and nitrogen.