Long-term in situ moisture conservation in horti-pasture system improves biological health of degraded land

In situ moisture conservation practices can conserve fertile topsoil and enhance available water in soil profile. We hypothesised that reclaiming degraded land ecologically through tree + pasture + in situ moisture conservation practices would significantly improve soil organic carbon (SOC) and health. Hence, the objectives were a) to identify changes in nutrient cycling enzymes and SOC status due to different in situ soil moisture conservation options in surface and subsurface soil layers, and b) to test the potentiality of soil enzymes to determine long-term nutrient availability. We conducted a long-term experiment involving aonla (Emblica officinalis) trees + pasture (Cenchrus ciliaris + Stylosanthes seabrana) + in situ soil moisture conservation measures viz. staggered contour trenches (T1), continuous contour trenches (T2), stone mulch (T3), vegetative barriers (T4), control (T5) and fallow land (T6) since 2007. Recommended dose of nitrogen (N), phosphorus (P) and potassium (K) were added to all treatments, except T6. SOC concentration increased by similar to 51 and 31% in T1 and T2, respectively, over T5 in surface (0-15 cm) soil. Culturable bacterial and fungal populations increased by similar to 20 and 95% in T1 over T5 in surface soil. Activities of all soil enzymes increased in Ti and T2 (ranging from 42 to 289%) over T5 and T6 in both surface and sub-surface (15-30 cm) layers. However, specific activity of phenol oxidase was similar to 25% lower for T1 than T6, suggesting more efficient SOC sequestration in Ti. Moreover, geometric mean enzyme activity of T1 was similar to 65 and 33% higher than T5 and T3, respectively, in surface soil. Treated soil quality index (T-SQI) of T1 was similar to 184% higher than T5. Soil functional diversity was also similar to 1.24 and 1.22 times higher in T1 and T2 than T5, respectively. Peroxidase was the major C degrading enzyme in this ecosystem. Protease, urease and phosphatase significantly influenced N and P availability along with fruit and pasture yields. Importantly, similar to 96, 62 and 82% variability of SOC, N and P concentrations, respectively, could be attributed to their corresponding enzyme activities. Principal components analysis (PCA) revealed one-way operational role of soil enzymes. Thus, enzymes are potentially important for recycling nutrients from litters, root biomass of fruit trees and grasses to boost their availability in the long run. Adoption of horti-pasture system combined with moisture conservation practices and staggered contour trenches or continuous contour trenches ensured higher above ground biomass yield, SOC, nutrient availability and soil quality. Thus, long-term use of these practices could be recommended for reclamation and improving soil health and crop productivity of degraded lands of central India.