Effect of Nitrogen Source, Soil Type And Depth of Application on Ammonia Volatilization

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Osman, Ibrahim Ali
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A field experiment was conducted to study the effect of soil type and methods of fertilizer application the ammonia volatilization when three orders of Sudan soils (Aridisols, Vertisols and Entisols) were fertilized by three types of nitrogenous fertilizers; namely, (Aqueous ammonia, Urea and Ammonium sulphate) in Berber, Gezira and Shambat Gerf, respectively.These fertilizers were applied by three methods: superficial application with irrigation water and injection in depth of 5 cm and 15 cm at a rate of 200 kg N/ha. A closed system was prepared around the points of application to collect volatile ammonia gas on diluted sulfuric acid 0.25 N and ventilation was ensured by using a semi- permissible membrane called parafilm. Sulfuric acid was analyzed using steam distillation apparatus containing sodium hydroxide, and then titrated with hydrochloric acid.The effect of nitrogen fertilizers and soil type on the movement of nitrogen in the soil was studied after one month in soil samples taken from the place of application and the external edge of the design. The results indicated that the rate of ammonia loss by volatilization in Aridisols was lower than Vertisols and Entisols and this is attributed to the different climatic conditions. In Berber the experiment was carried out during winter when temperature is low, causing a decrease in volatilization decreased, while in Gezira and Shambat the experiment was carried out in summer, and high rate of ammonia loss by volatilization was observed in Entisols and this is may be ascribed to high silt content in this soil. The results demonstrated that surface application of nitrogen fertilizers increased loss of ammonia by volatilization more than in method of application since the fertilizers on surface is exposed more to heat that increase volatilization. In Vertisols and Entisols, the rate of ammonia volatilization decreased gradually from the first week to the fourth week. But in Aridisols, increased rate of volatilization occurred in the fourth week due to negative impact of cold season on the microbial growth which limits the hydrolysis of ammonium carbonate resulting in delaying of volatilization process. In Vertisols and Entisols, high rates of ammonia volatilization were noticed in aqueous ammonia more than in urea and ammonium sulphate due to the fast hydrolysis of aqueous ammonia compared with other types of fertilizers, while in Aridisols, the ammonia volatilization recorded inconsistent values which attributed to cold weather. The results showed that, in all treatments, ammonium content was lower in samples taken from the edge compared to those taken from the place of application. This is attributed to the difficulty in movement of positively charged ammonium which adsorbed on negative charges of clay, while the amount of nitrate in the edge sample was greater than in the sample taken from the place of fertilizers application. This is possibly due to the presence of the negative charge in the nitrate which may increase the ion exchange with calcium and other cations in soil.
University of khartoum