秸秆还田对土壤有机碳结构的影响

秸秆还田既可以缓解土壤污染问题又可以增加土壤养分及改善土壤结构从而提高土壤质量。研究秸秆还田后土壤有机碳结构的变化对了解碳周转规律、促进农业管理和生产以及环境可持续发展具有重要意义。选取3种性质差异较大的土壤,分别为红壤、褐土及黑土。实验分为对照处理和添加质量分数为5%的水稻秸秆的秸秆处理。土壤在温室条件下培养24个月,每4个月取样一次,测定土壤中总有机碳含量及采用碳1s X射线吸收光谱测定土壤有机碳分子结构及各类型有机碳含量。实验结果显示,(1)黑土中总有机碳含量最高,达29.5-32.5 g·kg^-1,是红壤的4.7-6.4倍,褐土的3.9-4.9倍。加入秸秆后,红壤、褐土及黑土中有机碳含量较对照分别显著增加124%-196%、60%-110%和21%-28%。(2)3种土壤的对照中,有机碳主要以脂肪碳、羧基碳和烷氧碳存在。这3部分有机碳占总有机碳的百分比在红壤、褐土和黑土中分别为69.1%-86.6、79.6%-88.5%和87.3%-90.3%。加入秸秆后,3种土壤中有机碳类型依旧是上述3种有机碳占主导。(3)秸秆处理使红壤和黑土中有机碳疏水性增强,提高土壤团聚体稳定性,对改善土壤结构起促进作用。(4)秸秆加入后,红壤和褐土中发生正激发效应,这两种土壤中有机碳结构简单、稳定性减弱;黑土中发生负激发效应,其中有机碳结构趋于复杂,稳定性增强。

Effect of Straw Mulching on Soil Organic Carbon Structure

Straw mulching can not only alleviate soil pollution but also promote soil quality by increasing soil nutrients and improving soil structure.The research of the changes of soil organic carbon structure after straw mulching has great significance to understand the law of carbon turnover,promote agricultural management and production as well as promote environmental sustainable development.In this study,three types of soils with dramatically different soil properties were selected,namely red soil,cinnamon soil and black soil.The experiment was divided into control treatment and straw treatment with 5%rice straw.The soil was incubated in greenhouse for 24 months and sampled every 4 months.The total soil organic carbon content was determined,moreover,the molecular structure and various types of organic carbon content in the soil were determined by carbon 1s X-ray absorption spectrometry.The results showed that:(1)the total organic carbon content in black soil was the highest,reaching 29.5?32.5 g·kg^?1,which was 4.7?6.4 times of that in red soil and 3.9?4.9 times of that in cinnamon soil.Compared with control treatments,the organic carbon content in red soil,cinnamon soil and black soil increased by 124%?196%,60%to 110%and 21%to 28%,respectively.(2)In the comparison of three kinds of soils,organic carbon mainly exists in fatty carbon,carboxyl carbon and O-alkyl carbon,occupying 69.1%?86.6,79.6%?88.5%and 87.3%?90.3%in red soil,cinnamon soil and black soil,respectively.After rice straw was added,these three types of organic carbon were still dominant in the three soils.(3)Rice straw treatment enhanced the hydrophobicity of organic carbon in red soil and black soil,which improved the stability of soil aggregates and promoted the improvement of soil structure.And(4)after straw addition,positive priming effect occurred in red soil and cinnamon soil,in which the organic carbon structure in these two soils became simple and stability was weakened.In contrast,negative priming effect occurred in the black soil,in which the organic carbon structure tended to be complicated and the stability was enhanced.