Earthworm density, casting activities and its impact on canopy soil nutrient profile under different aboveground vegetations

Efforts were made to assess the earthworm’s density and their casting activity under different surface plant stands (Citrus reticulata, Rosa indica, Citrus + Rosa, Tabernaemontana divaricata, Dalbergia sissoo, and Cynodon dactylon) at few natural and planted sites of a semiarid part of Rajasthan, India. The role of earthworm community in nutrient dynamics of different layers of canopy soils was also measured during this study. Results suggested a direct impact of aboveground vegetation cover on soil microclimatic conditions and earthworm density. The maximum earthworm population density and casts production was under mixed plantation, i.e., Citrus + Rosa (119.2 ind. m−2 and 2,127.27 gm m2, respectively), while T. divaricata supported the minimum earthworm density and casting activities. The population density and total casts production was in the order: C. reticulata + R. indica > R. indica > D. sissoo > C. dactylon > C. reticulata > T. divaricata. Earthworm casts and canopy soils (0–10 and 10–20 cm depth) under different plant stand were analyzed for organic C, total N, available P, and exchangeable cations (K+, Ca2+ and Mg2+). Earthworm casts collected under Citrus + Rosa showed the maximum level of organic C, total N, available P, and exchangeable cations (K+ and Mg2+). It is concluded that resource input by standing plant community directly affects the canopy soil quality and, thereby nutrient level in earthworm casts. This study suggested that aboveground vegetation pattern plays an important role to improve the nutrient level of canopy soils and belowground earthworm activities.