Field management practices in agroforestry systems influence organic carbon and biological properties of soil

Different multipurpose tree species integrated into agroforestry may exhibit variable effects on soil characteristics, which not only depend on planted tree species but also on tree management practices being adopted. In the present study, the effect of different tree management practices on soil organic carbon, dehydrogenase activity, microbial biomass carbon and potentially mineralizable nitrogen was assessed in three well-established agroforestry models viz. model 1: crown pruning management [three levels: 0 (unpruned), 50 and 75%] in Albizia procera, model 2: tree density management (three levels: 200, 400 and 800 trees ha−1) in Hardwickia binata, and model 3: in situ soil moisture conservation (SMC) measures [four levels: normal planting (control), stone mulch, deep basin and deep basin + deep ploughing] in Emblica officinalis-based agroforestry. The aim was to determine (1) whether tree management practices have any effect on soil biological properties, and (2) what levels of these management practices are desirable in selected agroforestry systems. We hypothesized that these practices will improve soil in terms of biological properties, with moderate levels being more beneficial. For the purpose, soil samples were collected from two sampling locations [rhizosphere (> 1.5 m from tree base) and the non-rhizosphere zone (outside the tree canopy i.e. < 5 m from tree base), and at each location, from two soil depths (0–15 and 15–30 cm). The findings revealed that unpruned trees of A.procera caused the maximum improvement in soil, followed by trees subjected to 50 and 75% crown pruning. The maximum tree density of H. binata (800 trees ha−1) yielded the highest values of the studied soil biological parameters, followed by 400 and 200 trees ha−1. The SMC measures adopted in E. officinalis had variable effects on studied parameters, with deep basin and deep basin + deep ploughing outweighing stone mulch and normal planting. The values of all the parameters were significantly higher in the rhizosphere as well as in the upper soil (0–15 cm). Conclusively, the study suggests that light crown pruning in A. procera, stocking of 400–800 trees ha−1 of H. binata, and deep basin and/or deep basin + deep ploughing SMC measures in E. officinalis may be adopted as desirable management practices for optimum soil biological health in the semi-arid region of Central India.