Effects of urea micronized sulfur combined with urease and nitrification inhibitors on nitrogen transformation, losses, and crop response

Abstract While fertilizers are vital for food production, their environmental and health impacts require continual advancement. This study explored new micronized sulfur-containing nitrogen fertilizers (UREA-ES) that offer potential benefits compared to traditional options. The objective was to understand the transformation and loss pathways of UREA-ES, such as 40-0-0-13 (UREA-ES40) and 11-0-0-75 (UREA-ES11) in two different soils. This study evaluated the transformation and loss pathways of nitrogen (N) from the above fertilizers with and without urease (UI) and nitrification (NI) inhibitors in comparison to urea. Results of the study showed that the UREA-ES fertilizers had lower and delayed ammonia (NH 3 ) volatilization compared to urea treatment (UREA). The use of UI with UREA-ES fertilizers reduced NH 3 volatilization losses more effectively than UI with UREA, indicating potential synergies between UI and sulfur (S). The hydrolysis of UREA-ES fertilizers was slowed down by the UI under both acidic and alkaline conditions, similar to UREA fertilizer. The coating of UREA-ES fertilizers with UI + NI significantly delayed NH 4 + nitrification. Coating UREA-ES fertilizers with UI or UI + NI delayed nitrate leaching losses, indicating prolonged N availability in the soil. These results were corroborated by a greenhouse sorghum study where UREA-ES fertilizers with UI or UI + NI led to higher total N uptake and higher grain yield than UREA fertilizer with UI or UI + NI. UREA-ES fertilizers also resulted in higher total S uptake by sorghum, indicating improved S nutrition. Overall, the study revealed UREA-ES fertilizers had significantly improved total N uptake by sorghum and had significantly higher grain yields, especially at lower N application rates due to decreased N losses. Both UI and NI showed potential benefits for UREA-ES fertilizers compared to traditional UREA, including reduced NH 3 volatilization losses, delayed nitrate formation, and enhanced N uptake by plants, resulting in increased grain yields, especially at the lower N application rate (75 kg N ha⁻ 1 ).