Effects of Conservation Tillage on Soil Organic Matter in Paddyrice Cultivation

27 Mar Effects of Conservation Tillage on Soil Organic Matter in Paddyrice Cultivation

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Abstract

研究使用常规犁耕-休闲(DTF), 常规犁耕-小麦(DTW), 保护耕作-休闲(CTF), 保护耕作-小麦(CTW)4个处理, 评价连续 实验 10a后保护性耕作对稻作区 SOM的影响。 结果表明:垄作、免耕和小麦种植的结合是稻作区一种较好的保护性耕作实践。 它不仅显著增加 SOM在土壤表层的聚集, 而且它也通过改变 SOM的组成和结构显著影响土壤胡敏酸的光谱和热解特性。 相 比其他处理, 垄作免耕(稻麦)在 0 ～ 10 cm土层拥有最多的 SOM含量, 但随着土层厚度的增加, 这一含量下降的也较为迅速。 垄作免耕(稻麦)土壤胡敏酸在波长 665 nm处的光密度为 0.122, 465 nm处为 0.705, 而常规平作(中稻)在这两个波长处却分 别为 0.062和 0.321。 垄作免耕土壤胡敏酸 DTA曲线在 360 ～ 365 ℃处放热峰的焓变值比常规平作低, 1000 ～ 1050 cm-1吸收峰 常规平作也比垄作免耕强。垄作免耕土壤腐殖质的氧化稳定系数增高, 表明长期垄作免耕土壤腐殖酸的缩合度增高, 芳构化程 度增强。 通过保护性耕作和作物实践可以管理稻田土壤, 维持充分的 SOM积累, 缓解土壤有机碳的丢失。

English Abstract

In this study, the effect of conservation tillage on soil organic matter (SOM) in paddy rice cultivation after 10 yr was investigated. Four treatments, disk till-fallow (DTF), disk till-wheat (DTW), conservation till-fallow (CTF) and conservation till-wheat (CTW) were used. The results indicated that the combinative application of no-tillage, ridge culture and wheat cultivation was a sound conservation practice in paddy rice cultivation. It not only significantly increased the concentration of SOM in the topsoil, but also affected optical and pyrolysis characteristics of humic acids (HA) through changing the composition and structure of SOM. At 0–10 cm, the greatest SOM content was in CTW, but declined sharply with depth, while in DTF, DTW and CTF the SOM content was not as high at the surface as in CTW, but did not decline as fast as in CTW. The oxidation stabilization of SOM was generally greater in no-tillage and ridge culture than that in disk till. The HA optical density in CTW at wavelength 665 nm and 465 nm was 0.122 and 0.705, while in DTF was 0.062 and 0.321, respectively. E 4 E 6 ratio in CTW was higher than that in the other treatments. The enthalpy capacity of the exothermal peak (360–365°C) for the HA DTA curve in no-tillage and ridge culture was lower than that in disk till, while the HA absorption peaks in 1000–1050 cm 611 presented the reverse trend. The oxidation stabilization coefficient of HA in no-tillage and ridge culture was higher than that in disk till, indicating that the polycondensation degree and aromatization of HA were stronger. These findings suggest that it may be possible to manipulate paddy soil through conservational tillage and crop practices, and thereby maintain adequate SOM concentrations, and mitigate soil organic carbon loss from soil to atmosphere.