Abstract
The application of urea in coffee crop has caused high losses of nitrogen (N) by volatilization, causing the low use and recovery of this nutrient. This low use of N may interfere in the growth and nutrition of the coffee crop and thus, influence the efficiency of the nitrogen fertilization. The aim of this work was to assess the growth, nutritional and physiological characteristics and the agronomic efficiency of the nitrogen fertilization with different nitrogen fertilizer technologies. The experiment was performed in a greenhouse in pots with a volume of 14 L. In each pot, it was performed the transplanting of two plants of coffee. The experimental design was entirely randomized, with four repetitions. The following nitrogen fertilizers were applied in the dose of 10g pot -1 , splitted in three applications with interval of 50 days: Conventional urea; ammonium nitrate; urea + formaldehyde; Polyblen Extend®; Polyblen Montanha®; Urea + polyurethane; urea + plastic resin; ammonium sulfate + CaCO3 and the control, without N application. After cropping, it was evaluated the growth, nutritional and physiological parameters. Afterward, it was calculated two agronomic efficiency index of the nitrogen fertilization. The highest values of plants height, the total dry mass of plants and leaf area in coffee seedlings were found with the application of Polyblen Extend®. This blend also provided higher accumulation of N in the leaf and the whole plant. The application of Polyblen Extend® provided higher agronomic efficiency and also enhanced the photosynthetic rate in the coffee plants.
Highlights
Among the nitrogen fertilizers most used in coffee cultivation, urea is the most prominent
The experiment was carried out in a greenhouse of the Department of Soil Science of the Federal University of Lavras (UFLA), in Lavras city, Minas Gerais, from June 2015 to January 2016. It was used a soil of clay texture, classified as Red Latosol (RL) (SANTOS et al, 2013) collected in the B horizon, in Lavras
Soil pH was determined in water, in the soil: water ratio of 1: 2,5; H+Al (Method Ca (OAc)2 at concentration 0,5 mol L-1, pH 7,0; Ca2+, Mg2+ and Al3+ exchangeable, KCl were extracted with 1 mol L-1 and determined by titulometry; P and K were extracted by Mehlich-1 and analyzed by colorimetry (P) and flame photometry (K); the organic carbon was determined by oxidation with potassium dichromate; Zn, Mn, and Cu were extracted by Mehlich-1 and determined by atomic absorption spectrophotometry
Summary
Among the nitrogen fertilizers most used in coffee cultivation, urea is the most prominent. The reaction of urea’s hydrolysis in the soil causes an increase of the pH in the region of the granule (DOMINGHETTI et al, 2016) This alkaline pH environment hinders the passage of ammonia (NH3) to ammonium (NH4+) by the absence of protons (H+ ions), which concentrate ammonia in this region and increase the loss by volatilization of N-NH3 (CHAGAS et al, 2016). These losses contribute to a decrease in nitrogen fertilizer efficiency and can reach values up to 40% of the total N that is applied (FARIA et al, 2014). One of the most studied practices to improve the efficiency of nitrogen fertilizers is the use of increased efficiency’s fertilizers, classified as stabilized, slow release and controlled release (AZEEM et al, 2014; CHIEN et al, 2009)
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