Field evaluation of ammonia emissions, yield performance, and profitability under four nitrogen fertilizers in vegetable cultivation

Abstract

Ammonia (NH₃) emissions from vegetable cropping systems represent a significant pathway for nitrogen loss, leading to soil acidification and atmospheric pollution. This two-year field study (2022–2023) investigated the impacts of four nitrogen fertilizers—urea (UR), ammonium sulfate (AS), composite fertilizer (CMP), and latex-coated urea (LCU)—on NH₃ emissions, crop yield, and economic viability in fields of potatoes and Chinese cabbage. NH₃ fluxes were quantified using a static chamber method, and a Random Forest analysis identified fertilizer type, soil temperature, air temperature, and soil moisture as primary factors influencing daily emissions. Partial dependence analysis revealed that soil moisture had a dual effect on NH₃ volatilization, with fluxes decreasing at 8–20 % but increasing again above 20 %. Compared to UR, AS and CMP significantly reduced cumulative NH₃ losses by 35.8 % and 49.5 % in potatoes, and by 80.3 % and 52.5 % in cabbage, respectively. LCU reduced NH₃ emissions in cabbage by 51.3 % but showed inconsistent effects in potatoes, likely due to soil moisture and coating degradation. Economic analysis revealed that AS provided the highest net benefit in potato production, increasing profitability by 24.9 % over UR; this was followed by CMP at 11.5 % and LCU at 5.8 %. In contrast, UR was the most profitable fertilizer for cabbage, while LCU (−31.9 %) and AS (−29.9 %) reduced net returns due to higher costs and lower yields. These results highlight the necessity of selecting nitrogen fertilizers based on crop type and field conditions to simultaneously minimize NH₃ losses and optimize economic returns in vegetable production systems.