Effect of conservation tillage on soil quality in the piedmont plain of Mount Taihang

Conservation tillage is a viable option for sustainable agricultural development in the North China Plain. Yet few studies exist on the influences of conservation tillage practices on soil quality. The objective of this study was to investigate soil quality changes as related to the shift from moldboard plow to conservation tillage practices based on a long-term field experiment. The experiment was started in 2001 and included four winter wheat tillage treatments — moldboard plow without corn residue (CK), moldboard plow with corn residue (CT), rotary tillage with corn residue (RT), and no tillage with corn residue (NT). In 2007, the soil organic carbon (SOC) content, bulk density (ρ_b), water stable aggregate, water retention curve, soil saturated hydraulic conductivity (K_s) and soil microbial biomass C and N were measured after winter wheat harvesting. Soil samples were also collected in 2008 and analyzed for SOC, ρ_b and earthworm count. The results indicated no significant (P > 0.05) differences in stored SOC among the treatments. However, conservation tillage showed SOC stratification in the soil profile. This was indicated by higher SOC stratification ratios (SR) of 1.74~2.04 for RT and NT, and 1.37~1.45 for CK and CT. Earthworm abundance and microbial biomass C and N also increased under RT and NT treatments. Application of NT significantly (P < 0.05) increased soil ρ_b in the upper 0~20 cm soil layer, and also improved soil aggregate stability (measured by mean weight diameter). Whereas CT and CK treatments significantly increased the proportions of fissures (> 500 μm) and transmission pores (500~50 μm), NT treatment increased storage pores (50~0.5 μm) in the 0~5 cm soil layer. Tillage management increased soil K_s, field water capacity and plant available water content. The S index suggested that shift from conventional tillage to conservation tillage improved soil quality in the piedmont region of Mount Taihang.