作 者 ：区惠平,何明菊,黄景,朱桂玉,顾明华*,黎晓峰,沈方科
期 刊 ：生态学报 2010年 30卷 24期 页码：6812~6820
Keywords:paddy soil, no-tillage, rice straw manuring, humus, microbial activity,
摘 要 ：为了阐明免耕和稻草还田土壤固碳机制，研究了无稻草还田免耕（NT）、无稻草还田常耕（CT）、稻草还田免耕（NTS）和稻草还田常耕（CTS）对水稻不同生育期不同土层（0—5，5—12，12—20cm）土壤腐殖质形态、含量及微生物活性的影响。结果表明，免耕（NT和NTS）处理显著增加0—5 cm土层土壤游离松结态、联结态和稳紧结态腐殖质含量和游离松结态腐殖质占总腐殖质的比例，且免耕对土壤各结合态腐殖质含量的影响程度有随生育期的推后而增加的趋势；5—12cm和12—20cm土层土壤各结合态腐殖质含量和0—20cm各土层微生物活性有减少趋势；在水稻分蘖期免耕对微生物活性影响很弱，在水稻拔节—灌浆期免耕处理显著降低5—12 cm土层土壤微生物活性，相反，免耕却增加水稻成熟期0—5 cm土层的微生物活性；另一方面，稻草还田（CTS和NTS）显著提高土壤各结合态腐殖质含量，尤其是0—5 cm土层、游离松结态腐殖质及水稻生育后期；CTS处理显著增加分蘖期—孕穗期0—20 cm土层的呼吸强度，而稻草还田显著增加孕穗期—成熟期0—5cm土层的纤维素分解强度。可见，通过增加土壤腐殖质含量和各结合态腐殖质含量并改变微生物活性免耕有利于表土层碳的固定作用，而免耕与稻草还田相结合更有利于土壤碳的积累。
Abstract:Humus is important in increasing the biological stability of soil organic carbon, and agricultural management practices may significantly influence soil humus and microbial activity. However, how soil humus and microbial activity change with tillage practices is not well understood. Therefore, the effects of no-tillage without rice straw manuring (NT), conventional tillage without rice straw manuring (CT), no-tillage with rice straw manuring (NTS) and conventional tillage with rice straw manuring (CTS) on the contents of total and different forms of humus and microbial activity at different soil layers (0-5, 5-12, 12-20 cm) at different growth stages of rice plant were studied in this study. Result indicated that no-tillage (NT and NTS) not only increased the contents of total and different forms of soil humus but also increased the proportion of loosely-combined humus to total humus at the 0-5 cm soil layer, but it tends to reduce the contents of total and different forms of humus at the 5-12 cm and 12-20 cm soil layers and soil microbial activities at the 0-20 cm soil layer. The contents of total humus, loosely-combined humus and tightly-combined humus at the 0-5 cm soil layer in NT treatment was not significantly higher at the tillering stage compared to those in the CT treatment. In contrast, the contents of total and different forms of humus in both NT and NTS treatments were significant higher (P<0.05) than those in CT and CTS treatments during the elongation to ripening stage. The microbial activity in response to the treatments varied during the growth stage of the rice plant. Compared to the conventional tillage treatments (CT and CTS), the no-tillage treatments significantly decreased the microbial activity at the 5-12 cm soil layer during the elongation to filling stage, increased it at the 0-5 cm soil layer at the ripening stage, and had no significant difference at the tillering stage. Rice straw manuring treatments (CTS and NTS) significantly increased the contents of total and different forms of soil humus, especially loosely-combined humus, and such effect was much significant at the 0-5 cm soil layer during the late growth stage for NTS treatment and during the early growth stage for CTS treatment. In addition, rice straw manuring increased soil respiration intensity significantly during the tillering to booting stage for CTS treatment and at the ripening stage for NTS treatment, and it promoted soil cellulose decomposition intensity at the 0-5 cm layer during the booting to ripening stage for both NTS and CTS treatments. It was evidenced that soil microbial activity was promoted during the whole growth stage of rice plant under CTS and during the late growth stage of rice plant under NTS. These results suggest that no-tillage treatment can effectively protect soil organic carbon in different forms of soil humus, thus it increased the organic carbon content substantially. Moreover, the no-tillage treatment reduced soil microbial mineralization, thus it significantly mitigated CO2 emission from agricultural soils. Therefore, the no-tillage can improve soil organic carbon sequestration in the surface soil by elevating the contents of total and different forms of humus and modulate the microbial activity, while the no-tillage combined with rice straw manuring can increase soil carbon accumulation.
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