Effects of Carbon-Based Fertilizer on Soil Physical and Chemical Properties, Soil Enzyme Activity and Soil Microorganism of Maize in Northeast China

The soil environment is an important factor that affects the growth of maize. Our study discusses the effect of carbon-based fertilizer on the rhizosphere soil microenvironment. Xianyu 335 and Jingke 968 maize varieties were selected, and six treatments were set up as follows: no fertilizer, chemical fertilizer, or carbon-based fertilizer (3 t/hm2, 3.75 t/hm2, 4.5 t/hm2, and 5.25 t/hm2). The results showed that the carbon-based fertilizer significantly reduced the soil pH value in the late growth stage. Carbon-based fertilizer can significantly improve the conductivity of soil solution. On 8 July (jointing stage), the conductivity of the two varieties of soil was the highest at 3.75 t treatment, 259.38% and 169.26% higher than that of chemical fertilizer, respectively. Carbon-based fertilizer significantly increased the soil carbon flux. The soil carbon flux of Jingke 968 showed a trend of first rising and then falling with the increase in the application amount of carbon-based fertilizer. On 8 July (jointing stage) and 28 July (tasseling stage), the 4.5 t treatment reached the maximum value, and on 16 August (early filling stage) and 4 September (waxy stage), the 3.75 t treatment reached the maximum value. Carbon-based fertilizer significantly increased the content of nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium in the topsoil. Carbon-based fertilizer had a significant effect on soil enzyme activity and significantly increased soil neutral phosphatase activity in the late growth stage. On 16 August (early stage of grouting), β-Glucosidase activity was significantly higher in 3 t and 3.75 t treatments than other treatments in Xianyu 335 and Jingke 968. The activity of α-Xylosidase reached the highest at 3.75 t. The activities of polyphenol oxidase and catalase reached their maximum at 5.25 t treatment on 4 September (waxy ripening) and 26 September (full ripening). Carbon-based fertilizer significantly increased the soil bacterial diversity index (Shannon index, ACE index and Chao1 index), but had no significant impact on the fungal diversity index, and significantly increased the abundance of soil bacterial and fungal populations.