The present study was realized in order to determine the type of soil and the suitability of pH to avoid the losses of nitrogen from leaching and volatilization, using three different soils: organic, clayish and sandy, pH: 6, 7 and 8 and four nitrogenous fertilizers: Urea, Ammonium sulfate, Ammonium nitrate and Potassium nitrate. The ammonium and nitrates were estimated by using a probe and an spectrophotometer. The present research was conducted in Agricultural Sciences Faculty (IASA I),

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... sity of the Armed Forces (ESPE), Ecuador. The leached soil samples were estimated for ammonium and nitrates after 1, 3, 7, 14, and 21days, using the probe after volatilization. The evaluation was carried out by using a static camera for the measurement of NH 3 , with10 ml of 2 % with H 3 BO 3 and covered with a plastic cover. The data generated was analyzed by the Michaelis-Menten mathematical model for the measurement of the speeds and maximum concentrations. For comparison, two different solutions of Ammonium sulfate and Potassium nitrate were measured by the probe, and the spectrophotometer and the results were analyzed by the statistical Z-score test. The most reliable method is the probe. In clayish and sandy soils with pH 6, present less concentration of ammonium and nitrate, respectively. The greatest loss by volatilization is observed in sandy soil and the pH 8 with ammonium nitrate.