连续周年轮作休耕对土壤团聚体稳定性及有机碳的影响

Effects of Continuous Annual Crop Rotation and Fallow on Soil Aggregate Stability and Organic Carbon

为探究连续周年轮作休耕对红壤团聚体稳定性及有机碳含量的影响,以坡耕地红壤为研究对象,采用湿筛法和重铬酸钾-浓硫酸外加热法分别测定水稳性团聚体和有机碳含量,分析了2020~2022年玉米-苕子-玉米轮作(M-V-M)、玉米-豌豆-玉米轮作(M-P-M)、玉米-冬闲-玉米(M-F-M)和周年休耕(F-F-F)这4个处理下土壤团聚体稳定性及有机碳含量变化特征以及两者间的相互关系.结果表明,在2021年和2022年中,F-F-F、M-V-M和M-P-M处理的>2 mm团聚体含量较M-F-M分别显著提高了67.01%~100.92%、29.71%~33.67%和29.68%~38.07%;2021年和2022年中F-F-F、M-V-M的团聚体稳定性参数显著高于M-F-M(P<0.05).M-V-M处理下的>2 mm团聚体含量、GMD(几何平均直径)和MWD(平均重量直径)及F-F-F处理的R_(0.25)(>0.25mm团聚体含量)、MWD和>2 mm团聚体含量随着轮作休耕年限的延长而增加,而F-F-F处理下1~2 mm和<0.25 mm团聚体含量随着休耕年限的增加而降低.绿肥轮作和休耕处理均能够提高SOC含量,且F-F-F和M-V-M处理的SOC含量随年限的延长而增加.相关性分析表明,所有处理下SOC含量与R_(0.25)呈极显著正相关,与GMD呈显著正相关;F-F-F处理下的R_(0.25)和GMD及M-V-M处理下的GMD和MWD均与SOC含量显著正相关.结果表明,连续周年轮作休耕有利于提高土壤大团聚体含量、团聚体稳定性和SOC含量,可为我国南方坡耕地红壤区推行合理的连续周年轮作休耕模式和水土流失防治提供理论依据.

In order to explore the effects of continuous annual crop rotation and fallow on aggregate stability and organic carbon content in red soil,the red soil in sloping farmland was taken as the research object,and the water-stable aggregates and organic carbon content were determined using the wet sieve method and potassium dichromate-concentrated sulfuric acid external heating method,respectively.The changes in soil aggregate stability and organic carbon content under the four treatments of maize-vetch-maize rotation(M-V-M),maize-pea-maize rotation(M-P-M),maize-fallow-maize(M-F-M),and annual fallow(F-F-F)from 2020 to 2022 and the relationships between them were analyzed.The results showed that in 2021 and 2022,the contents of>2 mm aggregates treated with F-F-F,M-V-M,and M-P-M were significantly increased by 67.01%-100.92%,29.71%-33.67%,and 29.68%-38.07%,respectively,compared with that treated with M-F-M.In 2021 and 2022,the stability parameters of F-F-F and M-V-M were significantly higher than those of M-F-M(P<0.05).The content of>2 mm aggregates,geometric mean diameter(GMD),and mean weight diameter(MWD)under the M-V-M treatment and R_(0.25)(>0.25 mm aggregate contents),MWD and>2 mm aggregate contents under the F-F-F treatment increased with the increase in fallow years,whereas the content of 1-2 mm and<0.25 mm under the F-F-F treatment decreased with the increase in fallow years.Both green manure rotation and fallow treatment could increase the SOC content,and the SOC content of F-F-F and M-V-M treatment increased with the extension in age.Correlation analysis showed that SOC content was significantly positively correlated with R_(0.25) and GMD under all treatments.R_(0.25) and GMD under the F-F-F treatment and GMD and MWD under M-V-M were significantly positively correlated with SOC content.The results showed that continuous annual crop rotation and fallow was beneficial to improve the content of soil macro-aggregates,aggregate stability,and SOC content,which could provide theoretical basis for the implementation of reasonable continuous annual crop rotation and fallow patterns and soil erosion control in red soil areas of sloping farmland in southern China.