Fig. 3

Effect of compost application with or without urea on soil NH₄ ⁺ (mg kg⁻¹) and NO₃⁻ (mg kg⁻¹) after 49 days of incubation. Bars with the same letters are not statistically different at P < 0.05. Bars represent the standard deviation of the mean (n = 3). T1: 500 g soil + 5000 kg ha⁻¹ compost, T2: 500 g soil + 5000 kg ha⁻¹ compost + 100 kg N ha⁻¹, T3: 500 g soil + 5000 kg ha⁻¹ compost + 200 kg N ha⁻¹, T4: 500 g soil + 5000 kg ha⁻¹ compost + 400 kg ha⁻¹