Abstract
Soil carbon content is an important ecosystem property, especially under the ongoing climate change. The stability of soil organic matter (SOM) is controlled by environmental and biological factors including anthropogenic-induced agricultural management change. However, understanding the effects of anthropogenic activities (e.g., intensive agricultural practices) on carbon stability of soil profiles remains a challenge. The objective of this study was to determine the changes in carbon stocks through soil profiles following agricultural management change from grain fields to greenhouse vegetable fields. The sampling sites were located in an intensive vegetable production area in northernChina. A total of 20 pairs of grain fields (GF) and adjacent vegetable fields (VF) within a distance of50 mwere selected. The results showed that soil organic carbon (SOC) storage increased by 10.6 mg C ha-1 in upper soil layers but decreased by 5.3 mg C hm2 indeeper soil layers due to large input of organic manure and chemical fertilizer following the conversion from GF to VF. Conversion to VF also led to increased dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations. Extremely higher input of chemical N fertilizer in the VF led to the soil C:N ratio decreased by 2.02 times and the -N leached to deeper soils increased by 3.7 times compared to that in the GF. The pH value and microbial biomass carbon (MBC) content were lower in the VF than in the GF. These results indicate that excessive nitrogen application as fertilizers might lead to deeper soil carbon depletion. Reducing nitrogen addition in intensive agricultural systems is thus necessary to reduce soil carbon loss and to maintain a relatively sustainable soil system.
Highlights
Recent studies suggest that anthropological activities are creating regional environmental issues including changes in the levels of soil nitrogen, phosphorus, pH, and atmospheric CO2 [1] [2]
Farmers are encouraged by local governments to convert grain fields (GF) to vegetable fields (VF) under the increasing consumer demand, which leads to potential increase in the farmers’ income
The objectives of the present study were to determine the changes in total soil organic carbon (SOC) and total N, the soil C:N ratio, and labile C pools (DOC and microbial biomass carbon (MBC)) following the land-use conversion from cereal fields to vegetable field systems and to quantify the relationships between labile C pools, total SOC and soil pH
Summary
Recent studies suggest that anthropological activities are creating regional environmental issues including changes in the levels of soil nitrogen, phosphorus, pH, and atmospheric CO2 [1] [2]. The effects of agricultural management change on soil carbon balance and stability, especially in deeper soil layers, have not been fully explored. The studies informed management strategies aimed at enhancing stability of soil OM and reducing CO2 emissions [3]. Farmers are encouraged by local governments to convert grain fields (GF) to vegetable fields (VF) under the increasing consumer demand, which leads to potential increase in the farmers’ income. Vegetable cultivation often requires more intensive management and greater inputs of fertilizers and more irrigation [4]. The increased fertilizer application accompanying management change from GF into VF could alter soil properties at different soil depths
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