Blends de fertilizantes de liberação controlada e ureia com inibidores de urease para cafeicultura

Abstract

Adopting technologies for nitrogen fertilizers reduces nitrogen (N) losses and ensures greater agronomic efficiency in coffee plantations. In this context, the objective of this study was to evaluate technologies for nitrogen fertilizers in the Coffea arabica L., applied at different N rates, and to observe their effects on N dynamics within the soil-plant-atmosphere system. The experiment was conducted in the municipality of Santo Antônio do Amparo – MG, during the 2022/2023 and 2023/2024 growing seasons. The experimental design was a randomized block design with three replications and four N sources: conventional urea, organomineral fertilizer, and two blends. Treatments were applied at rates of 200, 280, and 400 kg ha⁻¹ year⁻¹. Conventional urea was split into three applications, while the other fertilizers were applied in a single dose. The evaluated parameters included ammonia volatilization losses (N-NH₃), nitrous oxide (N₂O) emissions, nitrogen release assessment under field and laboratory conditions, leaf N content, yield, efficiency, and N export via grains and husks. For the laboratory nitrogen release test, the organomineral fertilizer released 97% of its N within seven days of the experiment's start. By day 196, blend 1 reached a release rate of 73%, while blend 2 released 84% of the applied N. In the field trials, the following results were obtained: by day 257, blend 2 and blend 1 had released 95% and 72% of their N, respectively, in the 2022/2023 season; by day 196, blend 2 and blend 1 had released 94% and 72% of their N, respectively, in the 2023/2024 season. Cumulative ammonia volatilization losses were influenced by the technologies in the following decreasing order over the two-year period: urea (99.1 kg ha⁻¹ year⁻¹) > organomineral (68.5 kg ha⁻¹ year⁻¹) > blend 1 (44.2 kg ha⁻¹ year⁻¹) = blend 2 (42.8 kg ha⁻¹ year⁻¹). Ammonia volatilization losses were reduced compared to urea, with values 40.49% lower for the organomineral fertilizer, 71.17% lower for blend 1, and 71.34% lower for blend 2 in the 2022/2023 season. In the second season (2023/2024), the reduction in losses was 19.61%, 36.91%, and 39.75% for the organomineral fertilizer, blend 1, and blend 2, respectively. The control treatment resulted in the highest N₂O emission fluxes (1405.8 g ha⁻¹) among the treatments evaluated, suggesting that, under the conditions of the experiment, the unfertilized soil contributed more significantly to N losses in the form of N₂O compared to the tested fertilizers. The observed leaf N content remained within the adequate range (25 to 30 g N kg⁻¹). Yield and efficiency were not influenced by the applied technologies and rates, presenting average values of 2618.5 kg ha⁻¹ (43.6 60-kg bags ha⁻¹) and 473.4 liters of harvested coffee per 60-kg bag. The total N export, considering both grains and husks, averaged 102.6 kg ha⁻¹.