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

Transformation of nitrogen (N) from different manure sources to available forms to promote food security in context of rising climate change is vital. Effect of manure (types, nutrients, high rates and application time) on soil N transformation requires further investigation. This study evaluated effects of three animal manures on soil N mineralization of sandy clay loam.
A 22-week field study in a Randomized Complete Block Design (three replicates) was conducted using dried Cattle, Goat and Poultry Manures (CGPM), applied at 5, 10, 20, 40, 60, 80, 120 and 150 t ha−1 once at onset of the study. Also, N15P15K15 (0.4 t ha−1) was incorporated in three splits of 2, 8 and 14 weeks after incorporation (WAI) of manures as reference. Soil NH4–N and NO3−–N were determined bi-weekly.
The results showed N release peaked at 10 WAI with 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 for CGPM, respectively. Initial rapid N release phase occurred at 0–4 WAI, NH4–N and NO3−–N increased averagely by 182, 183, 139% and 131, 175, 144% for CGPM, respectively. Declines occurred at 8, 14 and 22 WAI but reduction observed at 22 WAI tripled 8 and 14 WAI.
Conclusionsz: Application of NPK and all the manures provided highest soil NH4–N and NO3−–N at 12 WAI. High rates of CGPM were not injurious to these soil properties; hence this has implication for N to maximize plants uptake as well as decrease losses to environment.