Carbon, Nitrogen and Phosphorus Mineralization as Influenced by Type of Organic Residues and Soil Contact Variation in Vertisol of Central India

Soil organic carbon (C) and nitrogen (N) play a critical role in plant nutrient dynamics and crop yield performance under different soils. In this study, the amount of carbon (C), N and phosphorus (P) mineralization as influenced by type of organic residue and soil contact variation was studied for an incubation period of 75 days under controlled laboratory conditions. Different types of residues, viz. subabul residue (Leucaena leucocephala) (T1), biochar of subabul residue (T2) and FYM (T3), along with unamended soil with no residue constituted the three modes of application, viz. buried (t1), incorporated (t2) and surface applied (t3) treatments. Among all the treatments, subabul residue applied treatments showed highest rate of C mineralization in which surface applied (SA) treatments varied from 19.54 at 24 h to 239.55 mg CO2–C/100 g soil at 75 days followed by subabul incorporated (I) (17.04–237.8 mg CO2–C/100 g soil) and subabul buried (B) (15.91–225.5 mg CO2–C/100 g soil) treatments. Subabul incorporated (I) treatment showed lowest rate of mineralization of NO3–N, which varies from 0.010 and 0.613 mg kg−1 at 7 days to 4.640 and 10.03 mg kg−1 at 75 days after incubation followed by subabul buried (B) and SA treatments. These results will be useful in the selection of agriculture crop inputs and their proper placement in soils with respect to nutrient mineralization.