Urease and nitrification inhibitors with pig slurry effects on ammonia and nitrous oxide emissions, nitrate leaching, and nitrogen use efficiency in perennial ryegrass sward.

OBJECTIVE

The present study was conducted to assess the effect of urease inhibitor (hydroquinone [HQ]) and nitrification inhibitor (dicyandiamide [DCD]) on nitrogen (N) use efficiency of pig slurry for perennial ryegrass regrowth yield and its environmental impacts.

METHODS

A micro-plot experiment was conducted using pig slurry-urea 15N treated with HQ and/or DCD and applied at a rate of 200 kg N/ha. The flows of N derived from the pig slurry urea to herbage regrowth and soils as well as soil N mineralization were estimated by tracing pig slurry-urea 15N, and the N losses via ammonia (NH3), nitrous oxide (N2O) emission, and nitrate (NO3-) leaching were quantified for a 56 d regrowth of perennial ryegrass (Lolium perenne) sward.

RESULTS

Herbage dry matter at the final regrowth at 56 d was significantly higher in the HQ and/or DCD applied plots, with a 24.5% to 42.2% increase in 15N recovery by herbage compared with the control. Significant increases in soil 15N recovery were also observed in the plots applied with the inhibitors, accompanied by the increased N content converted to soil inorganic N (NH4+ +NO3-) (17.3% to 28.8% higher than that of the control). The estimated loss, which was not accounted for in the herbage-soil system, was lower in the plots applied with the inhibitors (25.6% on average) than that of control (38.0%). Positive effects of urease and/or nitrification inhibitors on reducing N losses to the environment were observed at the final regrowth (56 d), at which cumulative NH3 emission was reduced by 26.8% (on average 3 inhibitor treatments), N2O emission by 50.2% and NO3- leaching by 10.6% compared to those of the control.

CONCLUSION

The proper application of urease and nitrification inhibitors would be an efficient strategy to improve the N use efficiency of pig slurry while mitigating hazardous environmental impacts.