Emissões de gases de efeito estufa por fertilizantes nitrogenados em lavoura cafeeira irrigada

Abstract

Agricultural soils are the largest source of nitrous oxide (N2O) emissions to the atmosphere. This gas is produced in the soil during nitrification and denitrification reactions, impacting over climate changes and the destruction of the ozone layer. In Brazil, there is little scientific information regarding N2O emissions in coffee production areas, where the dose of applied nitrogen ranges from 200 to 600 kg ha-1 per year. The evaluation of nitrogen fertilization management practices that reduce environmental pollution and increase the efficiency in the use of N by the cultures, must be further studied under Brazilian conditions. One of the alternatives to mitigating N2O emissions and the loss of N in the form of ammonium (N-NH3) to the atmosphere is the use of slow and controlled release and stabilized fertilizers. In this context, the objective of this work was to evaluate N loss in the form of ammonium and nitrous oxide, as well as the emissions of carbon dioxide (CO2) and methane (CH4) after the application of conventional nitrogen fertilizers, stabilized fertilizers and controlled release fertilizers in irrigated coffee crop. The study was conducted in the municipality of Monte Carmelo, Minas Gerais, Brazil, in the agricultural year of 2012/2013, using a randomized blocks design with six treatments and four replicates. The treatments consisted of the application of 368 kg ha-1 of N (four plots of 92 kg ha-1 of N, with the exception of fertirrigation) applied to the shoot projection of the plants, using the following sources: 1) conventional granular urea (UR); 2) granular urea coated with 600 mg kg-1 of NBPT (UR+NBPT); 3) granular urea coated with elastic polymer (UR+PE); 4) organic compound + urea (25% of total N applied in the form of organic compounds and another 75% in the form of urea) (UR+CO); 5) cerrado (control: no fertilizer application) (CER) and 6) 11 applications of N in fertirrigation (FERT). The emissions of N in the form of nitrous dioxide followed the decreasing order: UR+CO (0.925 kg ha-1 of N) = UR (0.849 kg ha-1 of N) = UR+NBPT (0.817 kg ha-1 of N) >FERT (0.465 kg ha-1 of N) = UR+PE (0.425 kg ha-1 of N) > CER (0.064 kg ha-1 of N). The emissions of N in the form of ammonium followed the decreasing order: UR+NBPT (177.2 kg ha-1 of N) =UR (166.5 kg ha-1 of N) > UR+CO (116.9 kg ha-1 of N) = UR+PE (103.5 kg ha-1 of N) > CER (4.7 kg ha-1 of N) = FERT (4.4 kg ha-1 of N). The application of N in fertirrigation and in the form of urea coated with polymers cause lower emissions of N-N2O and NH3. The nature and manner of nitrogen fertilizer application do not influence methane and carbon dioxide emissions or coffee productivity.