Ammonium-nitrogen transformation and nitrogen retention in broiler manure supplemented with a soil amendment containing nitrifying bacteria

The effect of a soil amendment on ammonium nitrogen transformation and nitrogen retention in broiler manure was evaluated. Prior to incubation, broiler manure was mixed with autoclaved soil or non-autoclaved soil in different ratios to make 1 kg mixtures; broiler manure:non-autoclaved soil = 9:1, 5:5, and 1:9 or broiler manure:autoclaved soil = 9:1, 5:5, and 1:9. The non-autoclaved soil treatment reduced either numerically or significantly NH₄ ⁺-N concentration compared to the autoclaved soil treatment during the 8-wk incubation. Total-N concentration of the non-autoclaved soil treatments was lower than the autoclaved soil treatments from 4 to 8 wk. The lowest manure to non-autoclaved soil treatment (M:S = 1:9) had considerably more nitrite and nitrate; however, the higher ratio manure to non-autoclaved soil treatments (M:S = 9:1 and 5:5) had slightly higher total nitrite and nitrate levels compared to the same ratio of autoclaved soil treatments. The moisture level of the 9:1, 5:5, and 1:9 M:S treatments were approximately 70, 45, and 30%, respectively. The results indicated that nitrifying bacteria in the non-autoclaved soil reduced the ammonium nitrogen concentrations of poultry manure by converting NH₃ or NH₄⁺ to NO₂^- or NO₃^-. However, the higher moisture levels in treatments with greater manure to soil ratios (M:S = 9:1 and 5:5) created anaerobic conditions that allowed for denitrification and greater N losses.