Implication of land use shifting on land degradation and restoration potential of conservation agriculture in India's North-West Himalayan region

The soil organic matter is a crucial factor in determining soil characteristics and productivity; however various land management practices degrade or aggrade the soil health. The objective of this study was to look at the influence of land-use conversion on soil health by using the concept of stratification ratio (SR) of soil organic carbon (SOC) and total nitrogen (TN) and appraise SR as a predictor of SOC and TN stock and soil health for India's North-West Himalayan region. The research is oriented toward assessing the consequences of various land use regimes' impacts on SOC and TN depth distribution, storage, and stratification and, hence, identifying appropriate sustainable tillage techniques for the region. The research was accomplished in 2020–21 in the long-term experimental plot with four land uses, namely control [natural sal forest (Shorea robusta L.), conventional tillage (CT), reduced tillage (RT), and zero tillage (ZT)] in a rainfed system of north-western Indian Himalayas. A decrease of 79% in the mean weighted diameter of CT was observed after conversion from forest land to CT; however, the decrease was only 50% in the case of the adoption of ZT. Further, the surface soil (0–5 cm) SOC was significantly different from each other, with forest soil having the highest SOC (27.5 ± 0.21 g kg−1) and CT having the lowest SOC (11.0 ± 0.09 g kg−1). The stock of SOC and TN increased significantly with increment in soil depth, and among landuses, the highest SOM was observed with forest and the lowest with CT. Among the treatments, forest (56.56 ± 1.90 Mg ha−1) had significantly higher SOC storage than conservation agriculture (CA) (42.84 ± 0.27 Mg ha−1, ZT, and 41.41 ± 1.84 Mg ha−1, RT) and CT (41.33 ± 1.19 Mg ha−1) based on equivalent soil mass approach. For forest land use, except the surface layer (0–5:5–10), all the soil layers had SR >2, whereas, for ZT, the bottom two layers (0–5:20–25 and 0–5:25–30) had SR >2 and for RT, only the bottom layer (0–5:25–30) was having SR > 2. It was observed that the conversion of land use to CT reduced the SR of SOM drastically; however, by adopting CA, the SR had been restored to near normal in forest land use. The carbon pool index (CPI) was used to determine the effects of soil tillage and residue incorporation on soil quality improvement with respect to a sal forest. The CPI value increased significantly with an increase in soil depth for three land uses, and also, at each soil depth, the CPI followed the ZT > RT > CT trend. Thus, CA may be considered a viable alternative to CT for improving soil physicochemical parameters.