Liberação de nitrogênio da ureia com diferentes revestimentos

• Autor(a) principal: Campos, Odirley Rodrigues
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5512
• topic: Volatilização; Solução de solo; Hidrólise; Volatilization; Soil solution; Hydrolysis; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Urea is the most widely used nitrogen fertilizer in agriculture and its rapid hydrolysis in the soil can lead to significant losses by ammonia volatilization (N-NH3(g)) or by nitrate leaching (N-NO3 -). In order to reduce N losses emerged in the market several products represented by the slow or controlled release fertilizers and stabilized fertilizers. Work developed with traditional fertilizers that use monitoring of N-NH3(g) loss or losses as N-NO3 - do not provide direct information about the release rates and information about the N dynamics in soil. Usual methods of assessment coated fertilizers based on dissolution in water conditions differ greatly from those found in agricultural crops, especially by the influences of humidity, temperature, pH, microbial and enzymatic activity, organic matter and cation adsorption capacity of the soil. The dissolution of fertilizers and chemical reactions after the dissolution can print these changes in chemical characteristics of the soil solution, therefore the evaluation of the liquid phase of the soil can provide information regarding the release of nutrients from fertilizers. To evaluate the release of N in fertilized soil samples with coated ureas, we made two trials. In the first trial adaptations were made to collect soil solution (SS) by centrifugation method, we evaluated doses of N-urea (1 and 2 g kg-1), one treatment without N application and relative centrifugal force ( FCR: 1500, 2000, 2500, 3000 g). Collectors soil solution consisted of PVC pipe 70 mm in diameter, 100 mm high with one end closed. Inside the tube was placed a ring of PVC and this was placed on a perforated plate. The incubators were placed on the plate riddled during centrifugation. The incubators were constituted of recipient with a volume of 250 mL and perforated lid. Soil samples were kept inside incubators of pre-incubation to collect soil solution. The volume of the SS, pH, concentration of total-N and electrical conductivity (CE) were not affected by FCR used in the absence of fertilizer. The presence of fertilizers changed the SS volume collected, the CE and the content of total-N were also changed. The pH varied with FCR applied in treatments with dose 1 g kg-1, but was independent of the FCR with dose 2 g kg-1 (pH = 9,10). The dose 2 g kg-1 promoted the largest increase in the variables pH, N-total and CE. When applied 2 g kg-1 of N-urea the response curves for N-total and CE showed lower slope and higher volume collected with FCR of about 2500 g. In the second trial, the release of N from coated fertilizers and its dynamics in the soil solution and soil samples were evaluated in a soil of sandy loam texture, which received 2 g kg-1 of N-urea. After applying the fertilizer in the soil was incubated times ranging from 1 to 1296 h. To collect the SS used the component described above and FCR of 2500g. Additional treatments were maintained until 1530 h of incubation in them was collected weekly NH3 volatilization, used to estimate gaseous losses of N in the other treatments (1 to 1296 h). Also in these treatments was collected and the SS was evaluated soil where the concentration of different forms of N. The analysis procedures included the determination of N-urea, N-NH4 +, N-total and pH of the SS and soil. In the soil was determined concentrations of N-urea, N-NH4 + and N-total. The sum (N-total SS + Ntotal soil + N-NH3(g)) was assumed to be N released. The treatments were arranged in a factorial (7 + 1) x 9), seven fertilizer (U, UP1, UNBPT, USP2, USP3, USP4 and USP5), a control without nitrogen applied and nine incubation times ranging from 1 to 1296 h. Treatments were arranged in randomized blocks with four replications. The fertilizers were classified into three groups of different release patterns: G1 (U, UP1, UNBPT, averaging 94% of the N released until 64 h), G2 (USP2 and USP3, averaging 54% of N released up to 382 h) and G3 (USP4 and USP5, averaging 33% of the N released until 779 h). The dynamics of N in SS and soil was different between the groups, there were major transformations of urea-N to N-NH4 +, greater increases in pH and losses of N-NH3(g) for fertilizers G1 followed by those of G2 and G3. The maximum loss by volatilization (NVol) were on average 23% (G1, average time of 717 h), 15% (G2, average time of 1174 h) and 3% (G3, average time of 1296 h). The UNBPT was not effective in reducing losses NVol, but slowed in about three days the peak volatilization in relation to urea pearly. The UP1 was not effective in reducing N release and reduced losses of N-NH3(g). The soil solution analysis could differentiate fertilizers in relation to their ability to release N.