保护性耕作对土壤有机碳组分的影响

Effects of Conservation Tillage on Soil Organic Carbon Fractions

为了探讨土壤有机碳及活性有机碳组分对不同耕作措施的响应,在黄土高原半干旱区的定西市李家堡镇进行了长期田间定位试验,采用免耕、秸秆覆盖及小麦和豌豆轮作等保护性耕作措施,对0-5 cm,5-10 cm,10-30cm 3层土壤的有机碳(SOC)、易氧化有机碳(ROC)、微生物生物量碳(MBC)的动态进行了系统的研究。结果表明,与传统耕作相比,保护性耕作的3个处理均能不同程度地提高两种轮作次序下SOC,ROC,MBC的含量,这说明保护性耕作有利于碳的固定和生态农业的健康发展,其中免耕和秸秆覆盖两部分结合效果最佳。同时,各处理土层的含碳量均随土壤深度的增加而降低。相关分析表明,ROC,MBC,ROC/SOC,MBC/SOC对不同耕作措施产生的响应与SOC基本一致,它们可以作为对土壤SOC影响的评价指标,与SOC的相关系数大小排序依次为MBC>ROC>MBC/SOC>ROC/SOC,在表征土壤有机碳变化上它们比SOC更敏感,其灵敏度排序为MBC>ROC/SOC>MBC/SOC>ROC,因此,在ROC,MBC,ROC/SOC,MBC/SOC等指标中,MBC更要值得重视和采用。

In order to explore responses of soil organic carbon（SOC） and active organic carbon（AOC） to different tillage patterns, long-term field experiments have been conducted at Lijiabu town of Dingxi city,Gansu province in semi-arid area of the western Loess Plateau since 2001. Readily oxidizable carbon （ROC） and microbial biomass carbon（MBC） were considered as indicators of AOC, and were measured together with SOC in soil layers of 0--5 cm, 5--10 cm and 10--30 cm. Four different treatments such as no-till with straw cover （NTS）, conventional tillage with straw incorporated（TS）,no-till without straw cover（NT）and conventional tillage （T） were designed in a rotation system between spring wheat and field pea. It was shown that the conservation tillage patterns, e.g. NTS,TS and NT, increased the concentration of SOC, ROC and MBC as well as ratios of ROC to SOC and MBC to SOC. This suggested that conservation tillage was beneficial for carbon sequestration, by which to alleviate greenhouse influence. Thus, it should be recognized as the key approaches to sustainable agriculture and environment in semi-arid area. In both rotation sequences, NTS treatment showed the highest values in the concentration of carbon among the different tillage patterns; meanwhile, carbon fractions had a declining trend with the increasing depth along the soil profile. Correlation analysis showed that AOC indicator had the similar response to the longterm tillage patterns and was more sensitive than SOC. The correlation coefficients of them followed the order as MBC〉ROC〉MBC/SOC〉 ROC/SOC, while the sensitivity of them followed MBC〉ROC/SOC〉MBC/SOC〉ROC, so MBC was the best carbon indicator to choose.