Nitrogen fertilizers technologies as a smart strategy to mitigate nitrous oxide emissions and preserve carbon and nitrogen soil stocks in a coffee crop system

Abstract

The paper consolidates the role of conventional and stabilized N fertilizers used in coffee crop production in Brazil and their N₂O emissions in tropical systems. The experiment consisted of the combination of three fertilizers and five doses with four repetitions, totalling 60 experimental plots. The factors of the experiment were conventional urea (U), ammonium nitrate (AN), and urea + NBPT (U_NBPT), while the doses were 0, 150, 275, 400, and 525 kg ha⁻¹ year⁻¹ of N. The municipality is located in a region at 1100 m of altitude, 20°53′26.04″ S and 44°52′04.14″ W. A randomized block design with a 3 × 5 factorial scheme was used. This region, traditional in coffee production, has a tropical humid climate, classified as Cwa according to the Köppen scale, with temperate summer and dry winter. U_NBPT and the ammonium nitrate mitigated the N₂O emissions by 50.6% and 78.5%, respectively, in comparison to the conventional urea. High C stocks were found in the 1 m soil layer, from 117 to 162 t ha⁻¹ of organic C, indicating the importance of the soil as a C sink in coffee plantations. N stocks varied from 33 to 17 t ha⁻¹ of N but no differences among the treatments were found. Approximately 50% of soil C was in the 0–0.4 m layer as a consequence of the greater amount of plant biomass, nutrients, and biological activity. Soil C:N ratio in the entire layer varied from 4.2 to 9.2. Our results indicate that nitrification is the most predominant process of N₂O emissions. The standard EF proposed by the IPCC overestimates the N₂O emissions in the Brazilian coffee plantations and the emissions differ according to the N fertilizer technology. These coffee crop systems have an important ability to stock C and N in the soil.