关键词: 绿肥, 还田方式, 还田量, 有机碳组分, 碳转化酶, 黑垆土

Abstract:

【Objective】 The aim of this study was to explore the effects of green manure return to the field on the content of soil organic carbon components and the activities of carbon invertase enzymes in dry-crop wheat fields, so as to provide data support for the improvement of soil quality and the achievement of the goal of “carbon neutrality”. 【Method】 The green manure return field experiment in a 5-year rotation system of hairy vetch (Vicia villosa Roth)-winter wheat (Triticum aestivum L.) and forage rape (Brassica napus L.)-winter wheat was conducted on a typical black clay soil in the Longdong dry loess area of Gansu Province. Soil organic carbon (SOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC) content and β-1,4-glucosidase (βG), cellobiose hydrolase (CBH), β-xylosidase (βX) geometric mean enzyme activity (GMEA) activities were analyzed in four soil layers of different stages of winter wheat after the mulching and overturning of hairy vetch, forage rape. 【Result】 The method of green manure returning to the field had a significant effect on the content of soil organic carbon components and the activities of CBH and βX. Compared with mulching, hairy vetch and forage rape overturning were able to increase the content of soil SOC, EOC and MBC by 12.9%, 12.1% and 53.8%, while the activity of βG, CBH increased by 3.2% and 10.2%, respectively, and the most significant effect was found in the 20-25 cm soil layer. There were significant differences in soil labile organic carbon content and soil enzyme activities at different winter wheat growth period, in which soil EOC and MBC content reached the highest at the maturity and greening stage of winter wheat, respectively, and the activities of βG, CBH, βX and GMEA reached the highest at the booting stage of winter wheat. The soil βG activity had the most significant changes and highest in different return methods and it was the main enzyme participating in the soil carbon transformation process after green manure returned to the field. Soil carbon component content and carbon invertase enzyme activity differed significantly in different soil layers, and both decreased with the increase of soil depth. The type of green manure also significantly affected soil carbon components and enzyme activities, in which the SOC and MBC content and the activities of soil βG, CBH, βX and GMEA returned to the field by forage rape were 1.08, 1.21, 1.15, 1.23, 1.19, and 1.19 times higher than common vetch. Structural equation modeling indicated that the green manure return method affected SOC accumulation by regulating the cumulative decomposition rate, and could regulate soil pH, SOC and the accumulated decomposition rate of green manure affecting GMEA activity. SOC accumulation was more affected by the green manure return biomass more than return method, while the opposite was true for carbon invertase enzyme activity.【Conclusion】 Cultivating and overturning forage rape during summer fallow period significantly increased soil organic carbon components and carbon invertase enzyme activities in 0-25 cm soil layer, which was an effective measure for efficient resource utilization during summer fallow period in Loess Plateau.

Key words: green manure, return method, return biomass, organic carbon component, carbon invertase enzyme, black clay soil