耕作方式对稻田土壤有机碳转化的影响

摘要

为阐明免耕土壤碳转化过程对土壤同碳的影响,设计了4种耕作方式,包括稻草还田免耕(NTS)、稻草还田常耕(CTS)、无稻草还田免耕(NT)和无稻草还田常耕(CT),在水稻生育期分层(0~5、5~12和12~20 cm)采集稻田耕层土壤样品进行测定.结果表明,在0~5 cm土层,土壤有机碳、活性碳、热水提取碳水化合物、全酚和腐殖酸含量免耕处理(NTS、NT)均表现为随水稻栽培时间的延长而逐渐增加,且显著高于常耕处理(CTS、CT),稻草还田下土壤碳含量增加更加显著.5~12和12~20 cm土层土壤各形态碳含量在水稻整个生育期免耕处理虽然低于常耕处理,但差异不显著.0～20 cm土层不同形态碳含量免耕处理高于或相当于常耕处理;不同碳形态含量间呈极显著正相关关系,这些结果说明免耕和稻草还田有利于促进土壤0~5 cm土层土壤有机碳的转化和腐殖化,尤其腐殖化过程的促进有助于增加土壤稳定碳库,这对土壤肥力的提高和控制土壤温室气体排放、减缓温室效应具有重要的意义.%In order to elucidate the effect of conversion process of the soil organic carbon on carbon fixation,four tillage patterns including no-tillage with straw incorporated (NTS), conventional tillage with straw incorporated (CTS), no-tillage without straw incorporated (NT) and conventional tillage without straw incorporated (CT) were designed. Soil samples were collected in soil layers (0 -5,5 - 12 and 12 -20 cm) during rice growth period. The result showed that in 0 -5 cm layer,the content of organic carbon,active carbon, hot water-extractable carbohydrate, total phenol and humic were continuous increasing with the rice growth and were significantly improved under no-tillage (NTS and NT) in the whole rice growth period,but in 5 -12 and 12 -20 cm layers were lesser but had no significant difference between no-tillage and conventional tillage (CT and CTS). Correlation analysis revealed that there were significant positive correlation among differents carbon forms. These results indicated that no-tillage and straw incorporated were benefit for the organic conversion and humification in 0 -5 cm layer and improved stable carbon by elevating humification, which was much better for improvement of soil fertility and inhibition of soil greenhouse gas emissions.