Effects of land reclamation on the physical, chemical, and microbial quantity and enzyme activity properties of degraded agricultural soils

摘要

Purpose Land reclamation, as a measure of increasing cultivated land area, is being popularized in China in the past decades. However, the impact of land reclamation on soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry, microbial quantity, and enzyme activities has been rarely studied. The objective of this study was to know how land reclamation affected soil properties in agricultural soils. Materials and methods Soil samples were collected at 0-20, 20-40, and 40-60 cm depths before and after land reclamation of degraded soils in a village of southwest China. The samples were used to determine soil bulk density, porosity, moisture content, texture, pH, soil C, N, and P nutrient properties, microbial quantity, and enzyme activities in agricultural soils. Results and discussion The soil clay content was increased by 59.7%, while the soil organic matter (SOM), available phosphorus (AP), total potassium, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and activities of catalase and urease enzymes were decreased by 49.9, 83.4, 32.8, 20.3, and 47.9%, respectively, at 0-20 cm of the soil. The decrease of SOM contributed to the decrease of MBC and MBN at 0-20 cm after the land reclamation. The soil texture had better capacity of water and fertilizer retention. Medium sand (> 0.25 mm) content, AP, the ratio of C to N, and activities of catalase were decreased, but pH and the ratio of N to P were increased at 20-40 and 40-60 cm. The clay content, medium silt (0.006-0.01 mm), total N, and quantity of fungi and actinomycetes were increased at 40-60 cm after the land reclamation. Conclusions Soil nutrient and enzyme activities at 0-20 cm were decreased but soil total microbial biomass was not disturbed at 0-20, 20-40, and 40-60 cm depths, after the land reclamation. The decrease of soil organic matter at 0-20 cm contributed to the decrease of MBC and MBN affected by land reclamation activities. Therefore, topsoil requires better management to preserve soil nutrients and enzyme activities after land reclamation.