[Effects of Different Proportions of Ammonium Sulfate Replacing Urea on Soil Nutrients and Rhizosphere Microbial Communities].

In order to investigate the effects of ammonium sulfate, an industrial by-product, on soil nutrients and microbial community when applied in different proportions instead of using urea as nitrogen fertilizer, a pot corn experiment was conducted. A completely randomized block experimental design was used, with a total of five treatments:CK (no fertilization), U₁₀S₀ (100 % urea), U₈S₂ (80 % urea + 20 % ammonium sulfate), U₆S₄(60 % urea + 40 % ammonium sulfate), and U₀S₁₀ (100 % ammonium sulfate). The basic physical and chemical properties of soil and the dry weight of maize plants were determined by conventional methods, and microbial sequencing was performed using the Illumina NovaSeq platform. The experiment results showed that:① In each growth stage of maize, the pH of soil treated with fertilization (7.85-8.15) was decreased compared with that of CK (8.1-8.21), and the pH showed a decreasing trend with the increase in ammonium sulfate content. ② The soil available nitrogen content increased gradually with the increase in the ammonium sulfate ratio at each growth stage of maize. Compared with that in the CK and U₁₀S₀ treatments, the ratio in the U₀S₁₀ treatment increased 30.56 % to 63.68 % and 13.22 % to 38.43 %, respectively. The variation trend of organic carbon content was opposite to that of available nitrogen (U₈S₂ > U₆S₄ > U₀S₁₀), and the addition of ammonium sulfate was still higher than that of U₁₀S₀ at other growth stages except for the seedling stage. ③ The protease activity of all fertilization treatments was higher than that of the control, and the protease activity was gradually enhanced with the continuous growth of corn and the increase in the ammonium sulfate ratio. The protease activity of the U₀S₁₀ treatment was higher than that of the U₁₀S₀ treatment at each growth stage of corn, which increased by 10.54 %-100 %. Soil sucrase activity ranged from 0.04 to 0.24 mg·(g·24 h)^-1, and those in the U₀S₁₀ treatments were significantly higher than those in the U₁₀S₀ and CK treatments at all growth stages, increasing by 20.32 % to 99.16 % and 24.31 % to 79.33 %, respectively. ④ The species abundance of bacteria and fungi in maize rhizosphere under all fertilization treatments were lower than those under the CK treatment, followed by those under the U₁₀S₀ treatment. The species diversity trend of the bacterial community in the three treatments with ammonium sulfate replacing urea were U₈S₂ > U₀S₁₀ > U₆S₄, and that of fungi were U₆S₄ > U₈S₂ > U₀S₁₀. ⑤ The maize dry weight of the U₁₀S₀ treatment and U₀S₁₀ treatment was the highest, which was 39.47 % and 36.16 % higher than that of the CK treatment, respectively, but the difference was not significant. The Pearson model showed that the species abundance and diversity of soil rhizosphere fungi and bacteria were affected by relevant environmental variables, among which pH value and soil available nitrogen content were the most important factors affecting microbial diversity. In conclusion, when corn planting in calcareous brown soil, replacing urea with a certain proportion of ammonium sulfate can improve soil nutrients more than urea alone, which affects the growth and rhizosphere microbial community of corn to a certain extent and has a greater yield.