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Long-term impact of farming practices on soil organic carbon and nitrogen pools and microbial biomass and activity

Author:
Wang, Yi, Tu, Cong, Cheng, Lei, Li, Chunyue, Gentry, Laura F., Hoyt, Greg D., Zhang, Xingchang, Hu, Shuijin
Source:
Soil & tillage research 2011 v.117 pp. 8-16
ISSN:
0167-1987
Subject:
Festuca, Food and Agriculture Organization, carbon dioxide, carbon sinks, conventional tillage, farming systems, fractionation, grasses, grasslands, humid zones, long term experiments, microbial activity, microbial biomass, no-tillage, soil density, soil fertility, soil organic carbon, soil texture, sustainable agriculture, Appalachian region, North Carolina
Abstract:
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 0–15cm 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<1.0gcm⁻³ (from 1.53–3.39% to 0.80–1.09%), and increased the very heavy fraction with d>1.6gcm⁻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.
Agid:
502711