Reducing ammonia loss from urea and improving soil‐exchangeable ammonium retention through mixing triple superphosphate, humic acid and zeolite

Abstract

Ammonia losses from soil following fertilization with urea may be large. This laboratory study compared the effect of four different, urea-triple superphosphate (TSP)-humic acid-zeolite, mixtures on NH 3 loss, and soil ammonium and nitrate contents, with loss from surface-applied urea without additives. The soil was a sandy clay loam Typic Kandiudult (Bungor Series). The mixtures significantly reduced NH 3 loss by between 32 and 61% compared with straight urea (46% N) with larger reductions with higher rates of humic acid (0.75 and 1 g kg )1 of soil) and zeolite (0.75 and 1 g kg )1 of soil). All the mixtures of acidic P fertilizer, humic acid and zeolite with urea significantly increased soil NH 4 and NO 3 contents, increased soil-exchangeable Ca, K and Mg, and benefited the formation of NH 4 over NH 3 compared with urea without additives. The increase in soil-exchangeable cations, and temporary reduction of soil pH may have retarded urea hydrolysis in the microsite immediately around the fertilizer. It may be possible to improve the efficiency of urea surface-applied to high value crops by the addition of TSP, humic acid and zeolite.

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

“…This observation was consistent with that reported by Ahmed et al [6,7] Interestingly, NH 3 loss was not significantly reduced with increasing amount of HA. There was a significant accumulation of NH 4 + in 0-1.5 cm depth for the treatments with HA compared with urea alone (Table 3) except for T2.…”

“…The effect of treatments on the pH of the mineral soils after 16 days of incubation was generally neutral (Table 4). This observation was similar to those reported by Ahmed et al [7,8] At 0-1.5 cm, the soil pH for the treatment with HA was significantly low compared with urea alone. All the treatments had no significant effect on the contents of exchangeable Na, Mg, K and Ca, but for Na the concentration increased with increasing amount of HA for 0-1.5 cm (Table 5).…”

“…Except for T0, the maximum NH 3 loss occurred on the second day of incubation. After the second day of incubation, there was a general decline in loss until day 16 when NH 3 loss was about 1% of the N added in the form of urea [5][6][7] .…”

“…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.…”

“…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] .…”