Abstract: Taking the vegetable garden soil in Shaoyang city as the research object, the effects of nitrogen and phosphorus addition on soil fertility were studied to provide the basis for rational fertilization of vegetable garden soil in Shaoyang city. By setting up three different fertilization treatments, which were single nitrogen application, single phosphorus application and N-P ratio column addition, the changes of soil organic matter, pH value and water content before and after the addition were measured, and their effects were analyzed. The results showed that the water content of N group decreased by 46.4%, and that of P group increased by 55%, but there was no significant change in N + P group; in the short term, N application alone could reduce soil water content and improve soil particle structure, but in the long term, N + P application was more conducive to soil water content balance. In the short term, the application of chemical fertilizer would not make the soil pH change significantly, but the soil pH would increase due to the influence of topography. Short term fertilization could increase the content of soil organic matter in 0~30 cm, and the three groups of soil organic matter increase degree was N group > N + P group > P group.

Key words: nitrogen and phosphorus addition, garden soil, pH, moisture content, organic matter