Effect of humic acid on ammonia volatilization from some calcareous soils

The objectives of this study were to compare the effect of three rates of humic acid (0, 2.5 and 5.0 g kg-1 soil) and N-urea (0, 60 and 120 mg N kg-1 soil) and mixtures of them on NH3, loss (volatilization) from two calcareous soils (Abul-Khasseb, silty clay soil, and Zubair, loamy sand soil). The use of humic acid significantly reduced NH3 loss and increased exchangeable NH4 + in both studied soils. The high total acidity of humic acid made the treatment the best in reducing N loss after incubation. Zubair soil showed more N loss than Abul-Khasseb soil due to their physical and chemical characteristics. The soil content of NH4 + and NO3 - increased significantly in both studied soils with increasing N rates. It can conclude that, humic acid, in general have great ability in controlling NH3 loss and retaining NH4 + in calcareous soils. It could be an economical efficient, practical and easiest way to control N loss.