Depthwise Distribution of Soil Organic Carbon and Nutrients under Some Tree Species after Seventeen Years of Plantation

Litterfall from trees enriches the organic matter and nutrient content of soil under the trees. The influence of four tree species was evaluated on soil organic carbon (OC), available macro- (N, P and K) and DTPAmicronutrient (Zn, Fe, Mn and Cu) content in the soil profile. Depthwise (0–15, 15–30, 30–60, 60–90 and 90–120 cm) soil samples were collected from 17 years old Leucaena leucocephala (subabul), Dalbergia sissoo (shisham), Acacia catechu (khair) and Acacia nilotica (kikar) spaced at 3 m x 3 m and adjoining open area considered as control, from PAU Research Station, Ballowal Saunkhri in sub-montane zone of Punjab. The samples were analysed for OC and nutrient content and the results stated that the accumulation of soil OC and nutrients was higher under trees than control. Soil OC and nutrient content decreased with increase in depth irrespective of tree species. The soil OC increased by 107% under shisham followed by kikar (92.4%) over control (3.30 g kg⁻¹) in the surface soil layer. The N content was higher under subabul (87.9 mg kg⁻¹ in surface layer); whereas P and K were higher under kikar (9.5 and 142 mg kg⁻¹, respectively in surface layer) than other tree species. Available micronutrients were higher beneath subabul and kikar than shisham and khair in the surface layer as well as whole soil profile. Therefore, the tree plantations can improve the nutrient availability in the soil profile.