Effects of the application of different nitrogen fertilizers on the ion compositions in solution of the greenhouse soil

An incubation experimental method was used to study the effects of application of different types of nitrogen fertilizers CO (NH2)2, NH4HCO3, and (NH4)2SO4 on the electrical conductivity (EC) and ion compositions and ratios in solution of a greenhouse soil. The addition of different types of nitrogen fertilizers only influenced EC of soil solution in the first week of incubation, after that the differences were not significant. The EC of soil solution was significantly increased by N application, indicating the significant contribution of nitrogen application to the accumulation of salts in the soil. The nitrate concentration in soil solution was increased with the application of N fertilizer and the incubation time. There were not significant differences in the nitrate concentrations in soil solution of different N fertilizer treatments. Different N fertilizer types only had some effects on NH4+-N concentration in soil solution in the first week of incubation, and then the differences among the different types of N fertilizers were not significant. The application of N fertilizer also increased the concentrations of K+, Na+, Ca2+and Mg2+ in soil solution, especially the concentration of Ca2+and Mg2+ ions; it was also the situation for the ratios of Ca/K and Mg/K in soil solution; however, the K+ activity ratio in solution remained constant during the incubation. It is concluded that the N application rates have significant effect on the ion balances between soil and solution interface. More attention needs to be paid to the effects of N application rates on the accumulation of salts in soil, and the leaching of K+, Na+, Ca2+ and Mg2+ from soil solution.