Xin Wang

Lime application to acidic soils is a common practice in agriculture to increase the soil pH and thereby improve soil nutrient availability. Urease inhibitors such as N‐(n‐butyl) thiophosphoric triamide (NBPT) are widely used to reduce ammonia (NH ₃ ) losses from urea. In Ireland, a substantial proportion of straight nitrogen (N) fertiliser is now applied as urease inhibitor–treated urea. Current guidance is to wait 3 months after liming before applying standard urea, but the use of standard solid urea is now restricted in Ireland and other European countries. For NBPT‐protected urea‐based fertiliser (NBPT‐urea), there is currently no research available to guide advice on the effect of the interval between liming and the application on NH ₃ emissions. As a result, there are uncertainties concerning the interval following lime application that should be recommended before applying NBPT‐urea. This study evaluated whether the interval between lime and NBPT‐urea application influences NH ₃ emissions in a grassland field. The initial soil pH of the site was 5.5; a requirement for 7.5 t ha ⁻¹ of lime was indicated. Lime was applied at four timings: 87, 28, 7, or 0 days before NBPT‐urea application. A NBPT‐urea treatment following no lime was also included as was a no‐lime control. The NH ₃ emissions from NBPT‐urea following liming were similar to those from NBPT‐urea following no liming regardless of the interval between liming and fertiliser application. Under the study conditions, the interval between lime application and NBPT‐urea application did not significantly influence the NH ₃ emissions from NBPT‐urea. We recommend that the current study results are validated by further field studies covering other soil types and ambient conditions.

Nitrification and urease inhibitors (NUIs) are chemical compounds that can reduce nitrogen loss and potentially enhance fertilizer nitrogen use efficiency when combined appropriately with nitrogen fertilizers. Many studies have highlighted their agricultural and environmental benefits, including improving crop yields, reducing nitrate leaching, and lowering nitrous oxide emissions. However, their unintended presence in the environment (e.g., surface water) and the food chain has raised concerns. Individual inhibitors exhibit different levels of risks and benefits that need to be evaluated separately. In this study, a risk–benefit ranking was conducted to prioritize 10 NUIs based on environmental exposure, toxicity, and benefit through the preference ranking organization method for enrichment evaluation. In general, the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) was identified as the most preferred, with a net flow value (φ) of 0.11 in the risk–benefit ranking of all NUIs, due to its significant agricultural and environmental benefits with low risk from its short half-life. This assessment was supported by the fact that nitrification inhibitors can sometimes increase ammonia emissions, reducing their overall effectiveness in improving nitrogen use efficiency as compared with urease inhibitors. Our results also illustrated that the nitrification inhibitor dicyandiamide (DCD) was a recommended alternative (φ = 0.08) among the evaluated nitrification inhibitors. This study assists stakeholders to balance the benefits and potential risks regarding the environment and human health issues associated with the application of NUIs in agriculture.