Ammonia volatilization from urea as affected by tropical‐based palm oil mill effluent (Pome) and peat

Metal-Urea-Montmorillonite Hybrid Incorporated with Citric Acid

“…Volatilized ammonia from the soil with and without perilla plant was collected by a closed-dynamic air flow method with slight modifications (Siva et al, 1999). The system consisted of an exchangeable chamber (30 × 30 × 20 cm) and a trap (250-mL Erlenmeyer flask) fitted with an inlet/outlet.…”

Reduction of Ammonia Loss from Urea through Mixing with Humic Acids Isolated from Peat Soil (Saprists)

“…The amount of ammonia loss was measured daily until the loss declined to 1% of the N added in the urea in a closed-dynamic air flow system method with modifications [5][6][7] . The system consisted of an exchange chamber with 500 mL conical flask and a trap (250 mL conical flask), both stoppered and fitted with an inlet/outlet.…”

“…According to Siva et al [5] , ammonia volatilization could be reduced by mixing urea with tropical peat soil but the cause of the reduction in ammonia loss due to humic substances such as humic and fulvic acids was not investigated. As it is well known, peat soils are high in organic matter which contributes to the availability of HA [10] .…”

“…Ammonia volatilization is most likely to occur even in acidic soils due to relatively high pH and also high concentration of NH 4 + ion around the microsite where the urea granules hydrolyses [3][4][5] . The pH in particular affects the equilibrium between NH 4 + ion and NH 3 (g) such that the relative concentration of NH 3 (g) increases from 0.1-1, 10 and 50% as the pH changes respectively from 6, 7, 8 and 9.…”

“…The pH in particular affects the equilibrium between NH 4 + ion and NH 3 (g) such that the relative concentration of NH 3 (g) increases from 0.1-1, 10 and 50% as the pH changes respectively from 6, 7, 8 and 9. It has been found that mixtures of urea and acidic materials can decrease ammonia loss while increasing the concentration of NO 3 − and NH 4 + ions [3,[5][6][7] According to Brady and Weil [8] , high concentration of NO 3 -and NH 4 + ions in the soil may not guarantee plant N use due to lack of good retention and leaching. Mixing Humic Acids (HA) with urea can reduce the pH and ammonia volatilization because they are high in CEC and total acidity thus providing good NH 4 + retention as well as preventing its loss through leaching [9] .…”