Abstract
Understanding the impact of tillage erosion on soil organic carbon (SOC) and nitrogen (N) fractions is essential for targeted soil conservation in mountainous and hilly areas. However, little is known about this issue. In this study, we selected a tillage erosion-dominated hillslope from the Sichuan Basin, China, to determine the effect of tillage erosion on particulate OC (POC), dissolved OC (DOC), light fraction OC (LFOC), ammonium N (NH4+-N), nitrate N (NO3−-N) and alkali-hydrolysable N (AN). Additionally, we investigated the microbial activities in relation to soil C and N dynamics, including soil microbial biomass, β-glucosidase and urease activities. Tillage erosion induced serious soil loss in upper slope positions and soil deposition in lower slope positions. The observations of the various labile OC fraction distributions across the hillslope suggest that tillage erosion exerts less impact on DOC and LFOC dynamics but a notable effect on POC. The distribution pattern in total organic carbon under tillage erosion mainly depends on POC redistribution. The POC redistribution is a major factor affecting microbial activities. The AN is more prone to the tillage erosion impact than NH4+-N and NO3−-N. Effective soil conservation measures should be taken to weaken the adverse impacts of tillage erosion on POC and AN redistribution in sloping farmlands.
Highlights
Understanding the impact of tillage erosion on soil organic carbon (SOC) and nitrogen (N) fractions is essential for targeted soil conservation in mountainous and hilly areas
Previous studies focus on the tillage erosion impact on total organic carbon (TOC) and total nitrogen (TN), and little is known about the fates of labile soil C and available N fractions under the effects of tillage erosion
We found that the particulate organic C (POC)/TOC values ranged between 8–44% compared with the values of dissolved organic C (DOC)/ TOC and light fraction organic C (LFOC)/TOC ranging between 1–8% (Table 1)
Summary
Understanding the impact of tillage erosion on soil organic carbon (SOC) and nitrogen (N) fractions is essential for targeted soil conservation in mountainous and hilly areas. Effective soil conservation measures should be taken to weaken the adverse impacts of tillage erosion on POC and AN redistribution in sloping farmlands. It is well known that temperate agricultural soils in mountainous and hilly areas are affected by tillage and water erosion at around the same order of magnitude[2]. Previous studies focus on the tillage erosion impact on total organic carbon (TOC) and total nitrogen (TN), and little is known about the fates of labile soil C and available N fractions under the effects of tillage erosion. More studies are needed to clarify how the labile C and available N fractions respond to tillage erosion to take targeted measures of soil conservation in mountainous and hilly areas. An artificial radionuclide from atomic weapons testing and emissions from nuclear power stations, 137Cs, is a well-established tracer for determining soil redistribution patterns (i.e., soil erosion and deposition) at field
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