Long-term effects of rainwater conservation measure on improving yield, runoff use efficiency and soil properties of horti-pastoral system on the degraded ravine lands of India

Ravine lands are known for network of gullies and worst form of terrain deformation. These lands are often causes high runoff (11–22 % of monsoon season rainfall), severe soil erosion (4-20 Mg ha⁻¹) and poor crop productivity. Low acceptance of cost-intensive conservation measures (e.g., levelling and terracing) in ravine lands system necessitates for developing low-cost conservation technologies like trenching. A long-term field experiment (2004–2014) was conducted to evaluate the impacts of staggered contour trenching (SCT) densities coupled with horti-pastoral system on various attributes of degraded ravine lands. The experimental setup was consist of four treatments: (i) control mini-watershed without trench (WC), (ii) mini-watershed treated with 139 trenches ha⁻¹ (WT₁), (3) mini-watershed treated with 278 trenches ha⁻¹ (WT₂), and (4) mini-watershed treated with 417 trenches ha⁻¹(WT₃). Results indicated that the yields of Phylanthus emblica fruit, Cenchrus ciliaris grass, and Dendrocalamus strictus were found to be the highest in WT₃ over WC by 126.3, 28.9 and 86.9 %, respectively with B:C ratio of 1:3.05. However, corresponding yield increase in WT₂ over WC was 50.0, 21.9 and 35.4 %, respectively with B:C ratio of 1:2.53. WT₁ registered the lowest increase. The highest effective rainfall use efficiency was recorded in WT₃ (47.5 %) followed by WT₂ (17.1 %) and WT₁ (7.5 %) over WC. The post-treatment values of hydraulic conductivity and sorptivity at table tops and gully beds of the control and treatment mini-watersheds were increased 1.6–2.6 and 1.3–1.6 times compared to pre-treatment values, respectively. The post-treatment values of the soil organic carbon was increased 0.8–2.2 folds than the pre-treatment values. Available-N, -P and -K content of the post-treatment at table tops and gully beds was also significantly increased by 18.3–25.5, 5.6–20.9 and 2.6–17.4 %, respectively. Overall, results highlighted that the SCT density of 417 trenches ha⁻¹ was the best conservation practices under horti-pastoral land use system. However, the optimum and economical SCT density was found to be 375 trenches ha⁻¹ by optimizing the net-profit per unit cost of the system. The findings of this study will be helpful to watershed managers and policy makers to reclaim and improve the sustaining productivity of degraded ravine lands.