Incubation Study of Kinetics and Mineralization Rate of Nitrogen in Organic Sources of Ultisol

Age-old traditional farming practices are generally followed by tribal inhabitants using locally available organic sources of plant nutrients. The aim of the present study was to determine the kinetics and rate of mineralization of different local organic sources of North East region of India. An incubation study of 100 days was carried out using locally available organic sources, i.e. farmyard manure (FYM; T₁), poultry manure (T₂), pig manure (T₃) and vermicompost (T₄) at the rate of 120 kg N/ha (considering recommended dose of fertilizer of rice as 120 kg N/ha). Bulk soil sample of Typic kandihumultis at 0–15 cm was collected from the College of Post Graduate Studies in Agricultural Sciences, Umiam, Meghalaya research farm and treated with organic sources and kept in an incubator at field capacity soil moisture and 25°C temperature. Observations were taken at 10 days interval up to 100 days of incubation (DOI). A control treatment (T₀) of no organic source was used for comparison. The results showed that the average nitrogen mineralization rate (N_min) of T₃ was highest (64.88%), followed by T₂ (57.77%), T₄ (42.98%) and T₁ (35.24%). The highest N_min rate of T₃ and T₂ was noted at 60 DOI as 79.37% and 76.10% respectively. At 50–60 DOI, total nitrogen, available nitrogen and nitrogen fractions (ammonical nitrogen and nitrate nitrogen) released were the highest irrespective of the organic sources. R² (coefficient of determinate) of first-order kinetics of all organic sources was found to be: 0.91 (T₃) > 0.90 (T₂) > 0.89 (T₄) > 0.88 (T₁), while R² of second-order kinetics was: 0.66 (T₃) > 0.65 (T₂) > 0.64 (T₁ and T₄). It has been concluded that T3 is the best organic nutrient source among the treatments considered for this study.