Abstract: As a high efficiency of water absorption material, polyacrylic acid potassium water-retaining agent and microbial agent can be mixed to significantly improve soil fertility. In this study, the polyacrylic acid potassium water-retaining agent was mixed with microbial agent to investigate their effects on soil moisture content, soil fertility and plant growth. Pot incubation tests were conducted to observe the growth of Pinus tabulaeformis and Medicago sativa. The contents of soil available N, P and K and soil moisture under these 2 plant species were tested and analyzed. Moreover, drought stress test was also carried out in the study. Results showed that the polyacrylic acid potassium water-retaining agent could be mixed with microbial agent to increase the contents of soil available N, P and K and soil moisture in varying degrees. Change trends of the contents of soil available nutrients under P. tabulaeformis and M. sativa were similar, but the optimal mix method was different for different plant species. For the annual P. tabulaeformis, the effect of high-concentration mix method on soil available N content was significant, and the effect of low-and moderate-concentration mix methods on the contents of soil available P and K was also high, and they were increased by 12%, 35% and 36% respectively. For M. sativa, the effect of high-concentration mix method on soil available N and P contents were significant, and the effect of low-and moderate-concentration mix method on soil available K was also high. The conditions of P. tabulaeformis and M. sativa growth and soil moisture level might be significantly improved when the moderate-concentration mix method was applied. For a defined area, it was needed to consider the actual conditions when using the water-retaining agent and microbial agent because of the different soil conditions, soil moisture level and nutrient level.

Key words: water-retaining agent, microbial agent, moisture and fertility preservation, plant growth, soil moisture content, soil fertility