Effect of Polymer-Coated Urea and Ammonium Nitrate Application on Nitrogen Behaviour in Sandy Soil and Yield Productivity

Abstract

A field experiment was carried out at El-Ismailia Agriculture Research Station farm, Agric. Res. Center (ARC), Egypt during two successive seasons (2015/2016). The institute farm is located at 30o 35' 41.9" N latitude and 32o 16' 45.8" E longitude. Wheat plants (Triticum aestivum L., CV. Giza 168) was planted during winter season (2015) and peanut plants (Arachis hypogaea) was planted during summer season (2016) in a sandy soil under sprinkler irrigation system, to improve the soil chemical properties, eliminate or reduce labor intensive of fertilizers losses, as well as increase in apparent nutrient recovery, through improving the nutritional status, minimize nitrogen loss, maintaining growth and yield of both wheat and peanut crops. Two sources of nitrogen fertilization were used, urea and ammonium nitrate with two rates (75% and 100% from the recommended dose) along with four rates of polymer (Hydrogel 0%, Hydrogel 1%, Hydrogel 2%, Hydrogel 3%) as a coating film material. Moreover, samples of the same nitrogen fertilizers were coated with the same four rates of polymers to be then incubated under laboratory condition to study the cumulative released percentage versus time, from both N-sources, along with the different rates of polymers; finally a field experiment was conducted. With regard to incubation experiment, results indicated that, the release of nitrogen from uncoated N-sources showed rapid and highly increase during the first two hours; the increase reached 94.35 % and 98.36% for both urea and ammonium nitrate respectively, uncoated urea being more responded as compared to uncoated ammonium nitrate. Generally, presence of polymer, as a coating material, caused slow gradual increase for soluble nitrogen as time goes up to 15 days as compared to without polymer treatment.The calculation of swelling ratio of hydrogel estimated that every one gram of hydrogel was swollen by uptake of 500 ml of water, this means that every 1 gram coating material from the used polymer absorbed 500 gm from the water. Also, Field Emission Scanning Electron Microscope noted that, the coated urea was smaller diameter, denser, more uniform and much smoother surface as compared to ammonium nitrate. On the contrary, the cross section of the coating shell of ammonium nitrate had a larger diameter, rough surface with large cavities along with both open and closed porosity.With regard to field experiment, results revealed that, the pH values in the soil after harvesting were significantly affected by both coated N-sources, as compared to uncoated treatments, for both tested crops; pH values increased significantly with time in presence of urea as compared to ammonium nitrate. Moreover, increasing the rate of nitrogen fertilization along with increasing the rate of applied polymer caused a significant increase in EC values during both tested seasons. Values representing nitrogen and potassium availability in soil, total contents (straw and grains or seeds) and yield components for both tested crops increased significantly in both co...