Studies On Coated Nitrogen Fertilizers And Nitrogen Fixation Adsorption Experiment

This thesis includes two parts, one is the preparation of coated nitrogen fertilizers and the evaluation of their slow-releasing characteristic, the other is the experiment of soil nitrogen-fixing. In the former experiment, coated ureas were made by coating bamboo-charcoal over normal urea, and then experiments including water dissolution, soil leaching, ammonia volatilization and pot culture were conducted to study the nutrients releasing characteristic and the fertilizer efficiency of bamboo-charcoal coated ureas and other nitrogen fertilizers. In soil nitrogen fixation experiment, zeolites, neat and bamboo-charcoal were chose to fix nitrogen which wasn't adsorbed by plants and soil colloid. The main results of this thesis are as follows:The results of water dissolution experiment showed that the nitrogen preliminary solubility rate of bamboo-charcoal coated ureas was less than normal urea obviously. The thicker the coating layer was, the slower its nutrient released. Moreover, fertilizer-water ratio, temperature and ionic concentration of extraction solution had significant effects on nutrient release of bamboo-charcoal coated ureas.Soil column leaching experiment was made to study the nitrogen leaching rate of bamboo-charcoal coated ureas and common nitrogen fertilizers. The results showed that the nitrogen leaching rate of bamboo-charcoal coated ureas and ammonium bicarbonate was less than those of potassium nitrate and urea remarkably. The relationship between nitrogen leaching rate and leaching time could be well described with polynomical curve and logarithmic curve, which showed that the coefficient (R²) had been high correlation. When fertilizing equal nutrition, the leaching loss of Ca²⁺, Mg²⁺, K⁺, Na⁺ caused by normal urea and bamboo-charcoal coated ureas remarkably less than those of potassium nitrate and ammonium bicarbonate. The soil pH and available nitrogen content were obviously different after soil column leaching with different nitrogen fertilizers. Soil media had significant effects on the nitrogen leaching amount.The ammonia volatilization behavior of bamboo-charcoal coated ureas and normal urea was studied using static adsorption method. With two application dosage of nitrogen fertilizers, total ammonia volatilization from two coating ureas decreased 16.66%～31.8% comparing with normal urea. Under the tested condition, the Elovich equation Yt=a+blnt could well describe the relationship between accumulated amounts of ammonia volatilization and time as high correlation coefficient. Soil moisture and temperature had significant effects on ammonia volatilization, total ammonia volatilization rose according to them.The results of pot culture experiment showed that the corn biomass fertilized with bamboo-charcoal coated ureas increased 12.8%～24.1% compared to normal urea, and the nitrogen utilization rate also increased 10.5%～16.9%.Compared to the single application of ureas or bamboo-charcoal coated ureas, the combined fertilization of common ureas and bamboo-charcoal coated ureas significantly increased the corn biomass and the nitrogen utilization rate. The result of soil nitrogen-fixing experiment indicated that the adsorption capacity order of tested adsorbents was:bamboo-charcoal(720mgN·kg^-1)> neat(570mgN·kg^-1)> zleolite (370mgN·kg^-1).Three adsorbents treatments could decreased the nitrogen leaching to understratum 49%～77.4% compared to contrast layer.