Soil carbon sequestration and soil quality change between no-tillage and conventional tillage soil management after 3 and 11 years of organic farming

The aim of this study was to evaluate the long-term effect of no-tillage systems in organic farming on soil carbon sequestration and soil quality, which is associated with nutrient availability. The experiment was conducted on a low-input organic farm since 2009, using a randomized complete block design with four replications. Two treatments, conventional tillage (CT) and no-tillage (NT), were tested. Soil samples were obtained after crops were harvested in 2012 and 2020 from four different soil depth layers between 0-30 cm, and the physical and chemical properties of soil samples were measured. Data were analyzed using ANOVA with Tukey tests (alpha = 0.05), while the correlation was analyzed based on Pearson correlation. At 0-2.5 cm and 2.5-7.5 cm depths, soil bulk density (BD) in the NT treatment was 30% and 8% lower, respectively, in 2012, and 25% and 14% lower, respectively, in 2020 compared with the CT treatment. The NT treatment could enhance the soil organic carbon (SOC) better than CT treatment at the same depth, sequestering a greater amount of carbon in the soil. Compared with the CT treatment, SOC concentration in the NT treatment was 76% and 12% higher, respectively, in 2012, and 103% and 38% higher, respectively, in 2020. In 2012, the SOC stock showed a significant difference between NT and CT treatments only at the 0-2.5 cm soil depth, with the value being 24% higher in the NT treatment than in the CT treatment. However, in 2020, the SOC stock was 50% and 19% higher in the NT treatment than in the CT treatment at 0-2.5 cm and 2.5-7.5 cm depths, respectively. The SOC also could significantly expand cation exchange capacity (CEC) and the availability of some nutrients in the soil. However, the relationship between was weak in 2020. Moreover, the NT treatment showed better progression of humification than CT. Finally, long-term NT systems in low-input organic farming could reduce soil bulk density and enhance soil carbon sequestration and soil quality. However, this system must be complemented with the conventional approach to maintain nutrient balance for long-term management.