@article{yi_wen-xia_tu_washburn_lei_hu_2014, title={Soil Carbon, Nitrogen and Microbial Dynamics of Pasturelands: Impacts of Grazing Intensity and Planting Systems}, volume={24}, ISSN={["2210-5107"]}, DOI={10.1016/s1002-0160(14)60027-8}, abstractNote={Management intensity critically influences the productivity and sustainability of pasture systems through modifying soil microbes, and soil carbon (C) and nutrient dynamics; however, such effects are not well understood yet in the southeastern USA. We examined the effects of grazing intensity and grass planting system on soil C and nitrogen (N) dynamics, and microbial biomass and respiration in a long-term field experiment in Goldsboro, North Carolina, USA. A split-plot experiment was initiated in 2003 on a highly sandy soil under treatments of two grass planting systems (ryegrass rotation with sorghum-sudangrass hybrid and ryegrass seeding into a perennial bermudagrass stand) at low and high grazing densities. After 4 years of continuous treatments, soil total C and N contents across the 0–30 cm soil profile were 24.7% and 17.5% higher at the high than at the low grazing intensity, likely through promoting plant productivity and C allocation belowground as well as fecal and urinary inputs. Grass planting system effects were significant only at the low grazing intensity, with soil C, N, and microbial biomass and respiration in the top 10 cm being higher under the ryegrass/bermudagrass than under the ryegrass/sorghum-sudangrass hybrid planting systems. These results suggest that effective management could mitigate potential adverse effects of high grazing intensities on soil properties and facilitate sustainability of pastureland.}, number={3}, journal={PEDOSPHERE}, author={Yi, Wang and Wen-Xia, Duan and Tu, C. and Washburn, S. and Lei, Cheng and Hu, S.}, year={2014}, month={Jun}, pages={408–416} }
 @article{wang_tu_cheng_li_gentry_hoyt_zhang_hu_2011, title={Long-term impact of farming practices on soil organic carbon and nitrogen pools and microbial biomass and activity}, volume={117}, ISSN={["0167-1987"]}, DOI={10.1016/j.still.2011.08.002}, abstractNote={Conventional agriculture with intensive tillage and high inputs of synthetic chemicals has critically depleted the soil C pools. Alternative practices such as no-tillage and organic inputs have been shown to increase soil C content. However, the long-term impact of these practices on soil C pools was not fully understood under humid and warm climate conditions such as the southeast USA. We hypothesized that a combination of sustainable production practices will result in greater microbial biomass and activity and soil organic C than any individual practice. To test this hypothesis, we conducted a long-term experiment examining how different farming practices affect soil C and N pools and microbial biomass and activities in a fine-sandy loam (FAO: Acrisol) in the southern Appalachian mountains of North Carolina, USA. The experiment was a randomized complete design with four replications. Six management treatments, i.e., tillage with no chemical or organic inputs (Control, TN), tillage with chemical inputs (TC), tillage with organic inputs (TO), no-tillage with chemical inputs (NC), no-tillage with organic inputs (NO), and fescue grasses (FG), were designed. Organic C and N pools and microbial properties in 0–15 cm soils were markedly different after 15 years of continuous treatments. Both no tillage and organic inputs significantly promoted soil microbial biomass by 63–139% and 54–126%; also microbial activity increased by 88–158% and 52–117%, respectively. Corresponding increases of soil organic C by 83–104% and 19–32%, and soil organic N by 77–94% and 20–32% were measured. The combination of no tillage and organic management increased soil organic C by 140% over the conventional tillage control, leading to a soil C content comparable to an un-disturbed grassland control. No tillage reduced the proportion of organic C in the light fraction with d < 1.0 g cm−3 (from 1.53–3.39% to 0.80–1.09%), and increased the very heavy fraction with d > 1.6 g cm−3 (from 95% to 98%). Organic inputs, however, had little impact on C distribution among different density fractions of the soil except light fraction in tillage treatment. Over all, no-tillage practices exerted greater influence on microbial biomass levels and activity and soil organic C levels and fractionations than organic inputs. Our results support the hypothesis and indicate that management decisions including reducing tillage and increasing organic C inputs can enhance transformation of soil organic C from the labile into stable pools, promote soil C accumulation, improve soil fertility and while mitigate atmospheric CO2 rise.}, journal={SOIL & TILLAGE RESEARCH}, author={Wang, Yi and Tu, Cong and Cheng, Lei and Li, Chunyue and Gentry, Laura F. and Hoyt, Greg D. and Zhang, Xingchang and Hu, Shuijin}, year={2011}, month={Dec}, pages={8–16} }