Avaliação da eficiência agronômica de novos fertilizantes nitrogenados granulados baseados no uso da ureia

Abstract

A study was conducted to evaluate the agronomic efficiency of nitrogen fertilizer with slow-release urea, measuring their losses by volatilization of NH3-N, N2O emission and recovery of fertilizer nitrogen applied as top dressing compared with commercioal urea to corn crop. All experiments were conducted at Embrapa Agrobiology. Firstly, the experiments were performed under controlled conditions in a greenhouse using soil layer of 0-10 cm of a haplic planosol. In the first experiment, the plastic trays were used as experimental units for evaluation of losses due to volatilization chambers with the aid of semi-open static free (SALE). Commercial urea was applied (UC), urea + KCl (UK), humic acid + urea (UH), urea + zeolitic sandstone (UZ) and urea + gypsum (UG) in two conditions of pH (5.4 and 6,5). Secondly, the other experiment was conducted using plastic pots containing the same soil samples as experimental units where they were planted three plants of Brachiaria decumbens. In this case, fertilizers were enriched with 15N, in two pH conditions too (pH 5,4 and 6,5). Treatments UZ and UK were more efficient in retaining N in the soil than the UC, with smaller losses through volatilization of NH3-N, and 20,2 and 15,8% on condition of lime and 22 and 17,2% when Liming did not occur, respectively. The UK fertilizer and UG showed overall increase of about 149 and 146% on dry biomass production at the end of the cycle on condition of pH 5,4. At pH 6,5 UG fertilizer showed yield increases of 149,3%. The accumulation of N in the plant and was 279,2 and 270,3 mg N.vaso-1 when no lime was applied to the UK and UG treatments, respectively, and the limed, 207.4 and 200,6 mg N. vaso-1 for the treatments UG and UH, respectively. Treatments UZ and UK had the highest recovery of applied N by plants, with values of 65,5 and 61,9% without lime, 60,2 and 45,7% with lime, respectively. Thirdly, other experiment was conducted at the experimental field at Embrapa Agrobiology in order to quantify the PNV, N2O emissions and efficiency of nitrogen fertilizer use (NFUE) slow-release by a corn crop on N balance Treatments consisted of field application of nitrogen fertilizers in coverage along the rows and a control treatment. Emissions of N2O were evaluated using static chambers closed. Was used fertilizers enriched with 15N in little plots for the assessment of NFUE. The treatments UZ and UK reduced the losses of N-NH3 by volatilization in approximately 18 and 14%, respectively. These losses corresponded to 32,3 and 35,7% of total N applied to soil. For N2O emissions the UK treatment showed the largest emission of N2O losses reaching values of 2.02 kgN.ha-1. The highest yield of grain were obtained by treatments that UG and UZ had a better response of grain production reaching values of 9666 and 9940 kg ha-1 respectively. To NFUE treatment UZ showed the highest values of N recovered reaching 67% of the total N applied system soil plant.