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We aimed to quantify the N losses through volatilization of the main conventional and stabilized N fertilizers applied in coffee plantations. Additionally, we also assessed microbiological attributes of the soil (microbial biomass carbon (MBC); microbial biomass nitrogen (MBN); microbial basal respiration (MBR); metabolic quotient (qCO2); urease, β-glucosidase, acid phosphatase, and arylsulfatase activities) and agronomic aspects of the crop (N content in the leaves and beans, yield, and N exportation by the beans). Treatments consisted of the combination of three fertilizers (ammonium nitrate - AN, conventional urea - U, and urea with N- (n-butyl) thiophosphoric triamide (NBPT) - UNBPT, and five doses of N (0, 150, 275, 400, and 525 kg ha-1 year-1 of N), with four replicates, totalling 60 experimental plots. In the two crop seasons evaluated, daily and cumulative losses of N-NH3 from the split fertilizer applications were influenced by the N fertilizer technologies. The application of U resulted in losses of 22.0% and 22.8% for the doses of 150 and 400 kg ha-1 year-1 of N. This means that 66 and 182 kg ha-1 of N-NH3 were lost, respectively, at the end of six fertilizations with U. UNBPT reduced urease activity and N-NH3 losses compared to conventional urea, avoiding the volatilization of 15.9 and 24.3 kg ha-1 of N. As for AN, N-NH3 losses did not exceed 1% of the applied dose, regardless of the weather conditions during the fertilization. Urease activity was higher on days of maximum NH3 volatilization. There was an effect of the N sources (NS), soil sampling time (ST), and their interaction (NS × ST) on the MBN and arylsulfatase activity. The N sources also influenced the MBC and the qCO2. A substantial amount of N was removed from the system by the beans and husks of the harvested fruits. Our study showed that N fertilizer technologies are interesting options to reduce N-NH3 losses by volatilization, increase N retention in the soil, and improve microbiological attributes and the sustainability of coffee production systems.

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 (UNBPT), 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. UNBPT 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.

The aim of this study was to quantify NH3-N losses from conventional, stabilized, slow-release, and controlled-release N fertilizers in a coffee field. The N fertilizers analyzed were prilled urea, prilled urea dissolved in water, ammonium sulfate (AS), ammonium nitrate (AN), urea + Cu + B, urea + adhesive + CaCO3, and urea + NBPT (all with three split applications), as well as blended N fertilizer, urea + elastic resin, urea-formaldehyde, and urea + polyurethane (all applied only once). NH3-N losses (mean of two crop seasons) were statistically higher for urea + adhesive + CaCO3 (27.9% of applied N) in comparison with the other treatments. Loss from prilled urea (23.7%) was less than from urea + adhesive + CaCO3. Losses from urea + NBPT (14.5%) and urea + Cu + B (13.5%) were similar and lower than those from prilled urea. Urea dissolved in water (4.2%) had even lower losses than those treatments, and the lowest losses were observed for AS (0.6%) and AN (0.5%). For the single application fertilizers, higher losses occurred for urea + elastic resin (5.8%), blended N fertilizer (5.5%), and urea + polyurethane (5.2%); and urea-formaldehyde had a lower loss (0.5%). Except for urea + adhesive + CaCO3, all N-fertilizer technologies reduced NH3-N losses compared to prilled urea.