秸秆添加量对棕壤有机碳固定与周转的影响

Effects of Straw Addition Amountson Organic Carbon Fixation and Turnover in Brown Earth

秸秆还田数量对不同肥力土壤有机碳库的影响存在一定差异,但由于测定技术的限制目前尚未有可靠的结果支撑。以沈阳农业大学棕壤长期(27年)施肥定位试验形成的高、低两种肥力土壤为研究对象,利用^13C标记的玉米秸秆为试验添加材料,采用砂滤管法将不同量秸秆分别添加到高、低肥力土壤中培养1年,通过定量分析两个肥力水平棕壤碳库中新、老碳含量随时间的动态变化,探讨玉米秸秆还田量对不同肥力土壤新、老有机碳固定与周转的影响。结果表明:秸秆添加量的提高使棕壤碳库的周转加快,显著增加棕壤有机碳含量及秸秆碳的贡献,降低老有机碳含量和碳库的稳定性,低肥棕壤固碳效率更高,受秸秆添加量影响明显,高肥棕壤固碳能力更强,有利于碳库的稳定。低肥有利于秸秆碳的固定,集中在添加秸秆后的180d内。高肥老有机碳的抗分解能力更强,且添加秸秆量越多,老有机碳的分解持续时间越长。高肥各处理中,<5%处理固碳效果较高;低肥各处理中,5%处理的新碳固定能力较强,10%处理的老碳固定能力较强。建议高肥土壤秸秆投入水平不超过5%固碳效果更佳,低肥土壤可在10%添加水平上加大有机碳的投入。研究结果为秸秆还田量对土壤碳库稳定的影响研究提供理论依据。

The organic ca rbon(C) pools of soils under different fertility levels would be affected by the amounts of straw returning to soil. However, there is no reliable result to support it due to the limitation of differentiating new added and native C. The purpose of this study was to investigate the effects of theamounts of maize straw returning on organic C fixation and turnover in soils under different fertility levels. The higher and lower fertility level soils were collected from the Long-Term(27 a)Located Brown Earth Experiment Station of Shenyang Agricultural University, Liaoning Province, China. The^13 C-labeled corn straw was added to soil and incubated for a year. The dynamics of new and old C contents in soils were quantitatively analyzed.The results showed that: Increasing the straw addition accelerated the turnover rateandfixationof organic C pools, significantly increased the organic Ccontent and straw-derivedC, decreased the soil-derived C and the stability of organic C pool in brown earth.The efficiency of C sequestration in lower fertility brown earthwashigher, and it was obviously affected by the amounts of straw addition. The ability of C sequestration in higher fertility brown earth was stronger and more beneficial to the stability of organic C pool. Thestraw-derived C was fixed more in lower fertility level soil, and concentrated in 180 days after adding straw.The decomposition resistance of soil-derivedC in higher fertility soil is better, and the decomposition duration of soil-derivedC would be longer with the amounts of straw added. The treatment of less than 5% straw addition was the best for organic C fixation in higher fertility soil, which was also the best for new Cfixation. Moreover, the treatment of 10% straw addition was the best for soil-derived C fixation in lower fertility soil. It is suggested that less than 5% straw addition inhigher fertility soil would be helpful to fix organic C in brown earth, while the input of organic Ccould be more than 10% in lower fertility soil. These results would provide a theoretical support to study soil C pool stability as affected by the amounts of straw returned to the field.