Ammonia volatilization and coffee productivity affected by nitrogen fertilizers of different technologies

Abstract

This work aimed to investigate the volatilization of ammonia (N-NH3) and the yield of coffee plants that received different types of enhanced-efficiency nitrogen fertilizers, defined as slow release, controlled-release, and stabilized fertilizers. The experiment was performed in a coffee farm in Lavras, in the state of Minas Gerais (MG) in Brazil, in the cropping seasons of 2015/2016 and 2016/2017. The thesis was divided in two experiments, with the first one being performed in the cropping season of 2016/17 in a randomized block design, containing 36 treatments, being four fertilizers: Conventional Urea, controlled-release coated urea with polymer (Ureia + Polymer), mixture of conventional urea and controlled-release urea (Blend), and urea coated with sulfur (Urea +S), 3 doses of nitrogen – N (190, 380, and 570 kg ha-1) with 3 replicates. The fertilization of Conventional Urea was divided into three applications, while the entire N dose was applied in a single application for the other fertilizers. The parameters evaluated were as follows: daily and accumulated volatilization rates of N-NH3 (only at the highest and lowest dose of N), N recovery field test, N and S concentration in leaves and coffee grain yield. Blend and controlled-release fertilizers showed lower peaks of volatilization in daily evaluation compared to Conventional Urea. Regarding the evaluation of accumulated volatilization over time, fertilizers applied at the dose of 570 kg ha-1 presented the highest accumulated losses by volatilization of N-NH3, reaching 45%, except in conventional urea that presented practically the same percentage of loss in both doses, 30%. There were no differences in N and S leaf concentrations and coffee yield among the treatment studied. The second experiment was carried out during the cropping seasons of 2015/2016 and 2016/2017. A completely randomized block design with 10 treatments and three replicates was used. The treatments were composed of the fertilizers applied in a sigle application (1x), in 2 (2x) or in 3 (3x) applications, as follows: Urea (3x); Ammonium Nitrate (1x); Ammonium Nitrate (3x); Urea with Organic Matrix (3x); Urea with Polyurethane (2x); Blend “a” = 50% Urea + 40% Multicote 2m + 10% Nitrocote 9m (1x); Blend “b” = 50% Ammonium Nitrate + 40% Multicote 2m + 10% Nitrocote 9m (1x); Blend “c” = 50% Urea NBPT + 40% Multicote 2m + 10% Nitrocote 9m (1x); Blend “d” = 50% Ammonium nitrate + 30% Multicote 4m + 20% Nitrocote 9m (1x); and the control (without N application). The parameters evaluated were as follows: daily and accumulated volatilization rates of N-NH3, agronomic efficiency, and productivity. The use of Ammonium Nitrate promoted the lowest (p<0.05) N-NH3 loss by volatilization. Urea and Blend “a” showed higher accumulated volatilization in the two evaluated harvests. Such result for the Blend “a” was due to the application in a single dose, as the amount of conventional urea in the composition of this blend is 50%. Regarding agronomic efficiency, Ammonium Nitrate, Blend “b”, and Blend “d” showed the best results. All treatments provided an increase in coffee yield, although the most relevant one were those that used Ammonium Nitrate (3x) and Blend “b” in both harvests. In conclusion, considering the conditions of the present study, the best efficiency of the fertilizer applied and the higher were reached by applying Ammonium Nitrate (3x) or Blend “b”.