AVAILABLE NITROGEN AND PHOSPHORUS RELEASE PATTERN FROM POULTRY MANURE, COW-DUNG AND BIO-GAS SLURRY

An incubation experiment was conducted to find out the decomposition pattern of organic manures and release pattern of available nitrogen (N) [ammonium nitrogen (NH₄-N) and nitrated nitrogen (NO₃-N)] and phosphorus (P) from the manures.  Manures used in the experiment were cage system poultry manure (CS-PM), deep litter system poultry manure (DLS-PM), cow-dung (CD) and bio-gas slurry (BS). Soil was amended with these manures @ 1 g 50 g^-1 soil. Microbial respiration (CO₂ evolution), NH₄-N, NO₃-N and available P were monitored over 30days at different day intervals. After 30days of incubation, 24.59, 22.46, 20.52 and 18.61% of the added C were decomposed from CS-PM, DLS-PM, BS and CD amended soil, respectively. N mineralization was highest at day 5 in CS-PM, DLS-PM and BS amended soil but in CD at day 10. All the manures showed marked immobilization after mineralization. Finally, net N mineralization was 118.03, 84.28, 69.80 and 52.13 µg N g^-1 soil in CS-PM, DLS-PM, BS and CD amended soil, respectively. Application of animal residues caused significant increase in P mineralization. Net P mineralizations were 47.21 µg, 32.79 µg, 19.70 µg and 15.63 µg P g^-1 soil after 30 days of incubation in CS-PM, DLS-PM, BS and CD amended soil, respectively.