Urea dissolution time in water and efficiency of foliar application in oat crops

Nitrogen via solid urea is easily lost by volatilization and leaching. This element, due to its easy absorption and translocation, shows the possibility of foliar supply. Knowledge of the dynamics of urea dissolved in water and foliar spraying on oats can improve use efficiency. The bjective of this study was to assess the urea dlution time under non-linearity of air temperature, and validate the technology of foliar application of urea dissolved in water in oat crops, considering different water volumes and urea (N) rates and the oat grain yield in different crop systems. The urea dissolution was carried out in laboratory, using a randomized block experimental design with four replications, in a 4x7 factorial arrangement, consisted of 4 water volumes (100, 200, 300, and 400 L ha(-1)) and 7 urea rates (0, 44, 88, 132, 164, 176, 220, and 264 kg ha(-1)). After determining the appropriate water volume for urea dissolution (300 L ha(-1)), a field experiment was carried out for foliar application, using a randomized block design with four replications, in a 2x7 factorial arrangement, consisted of application of two urea sources (solid and dissolved) and seven N rates (0, 20, 40, 60, 80, 100, and 120 kg ha(-1)). The water volume of 300 L ha(-1) dissolves the rates of urea, resulting in the expected oat grain yield for the nitrogen rates. The use of high rates increases the urea dissolution time; high air