Redução na volatilização de amônia derivada da uréia por ácidos húmicos produzidos de carvão de eucalipto

• Autor(a) principal: Paiva, Diogo Mendes de
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5425
• topic: Carvão; Urease; Nitrogênio; Charcoal; Urease; Nitrogen; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The economic and agronomic efficiency of urea, more nitrogen fertilizer consumed in world, is compromised by loss by volatilization of NH3, which can reach 80% of N applied. It has sought alternatives to reduce the volatilization of NH3, but these have given the rise in the cost of fertilizer and the results are uncertain due to many factors. The coating of urea with humic acids (HA) can be an efficient alternative for their cation exchange capacity high, of acid character and the high power buffer. Also, HA can be obtained from renewable source such as charcoal. This study aimed to evaluate the potential of HA obtained from charcoal from eucalyptus to minimize volatilization of NH3 derived from urea. Humic acids were obtained from charcoal of Eucalyptus grandis produced in carbonization temperature of 350 and 450 ºC (HA350 and HA450). We quantified the performance in the production of HA, which were characterized as the elemental composition, E4/E6 ratio (absorbance 465 nm / absorbance 665 nm), pH and total acidity (CTC). The influence of HA was evaluated in activity of urease. There were two trials which measured the volatilization of NH3, the first focuses on the urea mixed with increasing proportions of HA, obtained from the lyophilization of solution of urea with the HA, and the second focuses on the urea pearly commercial coated with 25 % HA. Both were conducted in a closed system dynamic (continuous flow of air of 0.25 L min-1) consisting of an incubation chamber (bottle of 0.34 dm3) and collecting units of NH3 (Erlenmeyer flasks with 60 mL of solution of H3BO3 20 %). Samples were taken every 24 h after application of urea during ten days, is replacing the units with new collector of NH3. The NH3 captured was quantified by potentiometric titration. Was characterized the kinetics of volatilization of NH3 through regression equations. The yield of HA was 257 g kg-1 and 541 g kg-1 for the coal produced at 350 and 450 °C, respectively. The HA350 showed higher total acidity and lower pH than the HA450. Both humic acids showed high stability, as evidenced in low E4/E6 relations. The urease activity was not influenced by HA. The lyophilization of the solution of urea resulted in the material powder. This fact, alone, caused a reduction of approximately 50% of the volatilization of NH3, masking effects of increasing doses of HA. The coating of urea granule with HA delayed the onset of volatilization. In addition, the peak of volatilization of NH3 occurred 72 h after application, while for the uncoated urea occurred at 48 h. HA promoted the lower rate of volatilization. However, only the HA350 was capable of significantly reducing the total volatilization of NH3, which can be attributed to its higher total acidity, which favors the formation and adsorption of NH4 +.