Analysis of the Effect of Modified Biochar on Saline–Alkali Soil Remediation and Crop Growth

To solve the problem of soil degradation in coastal saline–alkali land, three different types of biochar (rice straw biochar, magnetic biochar, and humic acid–magnetic biochar) were prepared to remedy the saline–alkali soil under different mixing ratios. The effects of biochar on the growth of crops in saline–alkali soil were explored through a pot experiment on Chinese cabbage. The experimental results showed that the soil leaching treatment combined with humic acid–magnetic biochar could effectively repair the coastal saline–alkali soil. After adding 5% humic acid–magnetic biochar, the content of soil organic matter was 33.95 g/kg, the water content was 13.85%, and the contents of available phosphorus and available potassium were 9.43 mg/kg and 29.51 mg/kg. After adding 5% humic acid–magnetic biochar, the plant height of Chinese cabbage was 9.16 ± 0.19 cm, and the plant germination rate reached 83.33 ± 5.54%. The incorporation of biochar could effectively increase the chlorophyll content and soluble protein content of pakchoi and reduce the soluble sugar content of pakchoi. The study analyzed the effect of different modified biochar on saline–alkali land restoration and crop growth and explored the action rule of hydrochloric acid magnetic biochar on saline–alkali land restoration, which has important practical value for improving coastal saline–alkali land.