Dynamics of soil nitrogen availability indices in a sandy clay loam soil amended with animal manures

Purpose Transformation of nitrogen (N) from differentmanure sources to available forms to promote food securityin context of rising climate change is vital. Effect ofmanure (types, nutrients, high rates and application time)on soil N transformation requires further investigation.This study evaluated effects of three animal manures onsoil N mineralization of sandy clay loam.Methods A 22-week field study in a Randomized CompleteBlock Design (three replicates) was conducted usingdried Cattle, Goat and Poultry Manures (CGPM), applied at5, 10, 20, 40, 60, 80, 120 and 150 t ha-1 once at onset ofthe study. Also, N15P15K15 (0.4 t ha-1) was incorporated inthree splits of 2, 8 and 14 weeks after incorporation (WAI)of manures as reference. Soil NH4 –N and NO3-–N weredetermined bi-weekly.Results The results showed N release peaked at 10 WAIwith highest NH4 –N (830, 400, 253 mg kg-1) and NO3-–N (316, 398, 250 mg kg-1) at 150, 60 and 60 t ha-1 forCGPM, respectively. Initial rapid N release phase occurredat 0–4 WAI, NH4 –N and NO3-–N increased averagely by182, 183, 139% and 131, 175, 144% for CGPM, respectively.Declines occurred at 8, 14 and 22 WAI but reductionobserved at 22 WAI tripled 8 and 14 WAI.Conclusions Application of NPK and all the manuresprovided highest soil NH4 –N and NO3-–N at 12 WAI.High rates of CGPM were not injurious to these soilproperties; hence this has implication for N to maximizeplants uptake as well as decrease losses to environment.