耕作方式对干旱绿洲滴灌复播大豆农田土壤有机碳的影响

为探讨不同耕作措施对不同层次土壤碳的影响,从而评价出滴灌条件下最有利于复播大豆农田固碳的耕作方式,于2012-2014年开展了冬小麦收获后土壤采取翻耕覆膜(tillage plough,TP)、翻耕(tillage,T)、旋耕(rotary tillage,RT)和免耕(no-till,NT)4种不同耕作方式的复播大豆田间试验,研究麦后不同土壤耕作方式对复播大豆农田0~100 cm土层土壤容重、总有机碳(soil organic carbon,SOC)及碳库管理指数(carbon pool management index,CPMI)的影响。结果表明,各处理土壤SOC和易氧化有机碳(easily oxidized organic carbon,EOC)含量随着土层的加深基本呈不断下降趋势。免耕、旋耕处理显著增加了表层0~10 cm土壤的SOC和EOC含量,而TP处理显著增加了耕层20~30 cm的SOC和EOC含量,60~100 cm土层TP处理的SOC含量显著低于其他处理,但各处理间EOC含量差异不显著;土壤容重与总有机碳含量呈显著负相关关系(P0.01);0~60 cm土层不同耕作方式CPMI平均值以免耕处理最高,分别比旋耕、翻耕覆膜、翻耕处理的增加了4.41%、9.90%、22.06%,表明免耕、旋耕能够提高0~60 cm土壤的总体CPMI,而耕翻覆膜显著提高20~30 cm耕层土壤CPMI值。该研究为干旱绿洲滴灌条件下选择最有利于复播大豆农田固碳的耕作方式提供了理论依据。

Effects of different tillage methods on soil organic carbon in soybean soil of drip irrigation in arid oasis

Abstract: In recent years, the climate warming has become the focus of global attention. Unreasonable soil tillage can lead to greenhouse effect. Reasonable soil tillage management measures can make farmland soil play some carbon sink function, which fixes soil organic carbon (SOC), and also effectively controls greenhouse gas emissions. Currently, researches about the influence of conservation tillage on organic carbon exist, but the most of them are focused on the soil surface, and more are concentrated in northern China dry rain-fed agriculture. There are very few studies about organic carbon content of deep soil profile and irrigated agriculture, especially under the condition of drip irrigation in Xinjiang. In today's background of advocating low carbon agriculture, this study was to investigate the effect of different tillage methods on soil organic carbon in 0-100 cm soil layer planted with summer soybean by drip irrigation in arid oasis, in order to evaluate what was the most beneficial cultivation way to carbon sequestration in soybean field. After the harvest of winter wheat, 4 different tillage methods including tillage plough (TP), tillage (T), rotary tillage (RT) and no-till (NT) were carried out to study the effect of different soil tillage methods on soil bulk density, total organic carbon (TOC) and carbon pool management index (CPMI) in 0-100 cm soil layer in multiple cropping soybean field experiment during 2012-2014. The results showed that the contents of SOC and easily oxidized organic carbon (EOC) increased and the depth of soil increased. NT and RT treatments increased SOC and EOC content significantly in the 0-10 cm soil. Among them, the SOC mass fraction of NT treatment was 13.619 g/kg, higher than RT, TP and T treatment by 5.08%, 14.36% and 17.04%, respectively. The EOC content was 2.92 g/kg, higher than RT, TP and T by 5.04%, 21.16% and 31.53%, respectively. The TP treatment increased SOC and EOC content significantly in the topsoil of 20-30 cm. Among them, the mass fraction of SOC of TP treatment was higher than T, RT and NT by 16.22%, 12.31% and 10.52%, respectively, and the EOC mass fraction of TP treatment was 5.78%, 8.18% and 23.96% higher than that of T, RT and NT respectively. There was significant difference in SOC content of in 60-100 cm soil layer, but there was no difference in EOC content between TP treatment and other treatments. Soil bulk density and TOC content had significantly negative correlation (P<0.01). Among different tillage methods, the NT's CPMI was the highest, and 4.41%, 9.90% and 22.06% higher than RP, TP and T respectively in 0-60 cm soil layer. The soil bulk density of each treatment increased gradually with the soil layer increasing, and under 30 cm depth, it increased slowly. The results showed that for the soil bulk density of 0-60 cm layer, the NT was the largest compared with other treatments, which was more obvious when being closed to the surface. The soil bulk density was relatively small in 0-30 cm soil layer for the rest of the treatment. The NT and RT treatment could improve the overall quality of CPMI in 0-60 cm soil layer and the tillage mulching significantly improved the CPMI in 20-30 cm soil layer. This study provides a theoretical basis for the selection of the most beneficial cultivation method to the carbon sequestration of soybean planting under drip irrigation in the arid oasis.