【Objective】Biochar has been shown to improve soil physicochemical properties and enhance crop yields. The results of previous studies on soil temperature were inconsistent, the changes of crop emergence rate under the change of biochar application rate were not analyzed in detail, and the relationship between crop emergence rate and soil physicochemical properties such as soil bulk density, temperature and organic carbon was neglected. Thus, it is important to estimate the most appropriate application rate of biochar for improving soil physicochemical properties and crop yield to provide a basis for field management. 【Method】In this paper, a salinization soil in south Xinjiang was researched and field cotton and sugarbeet growth experiments were carried out in plots under different biochar treatments (0, 10, 50, and 100 t·hm^-2) and combined with drip irrigation mode under plastic mulching. The improvement extent and influences of biochar application on soil physicochemical properties and crop germination rates were detailed investigated at the biochar application rates. The relationship between germination rates and soil physicochemical properties was further investigated and compared. 【Result】The results showed that the fluctuations of daily air temperature and solar radiation directly affected the fluctuations of soil temperatures in various depths with biochar applications. The increase of biochar application amounts significantly reduced the soil bulk density at the 0-30 cm depths, in which cotton and sugar beet decreased by 0-0.32 and 0.04-0.25 g·cm^-3, respectively. The application of biochar at 100 t·hm^-2 significantly increased the soil temperature at the 5 cm depth at different growth stages of cotton and sugar beet, but the application of biochar at 10 and 50 t·hm^-2 only significantly increased the soil temperatures of the 5 cm depth at seedling and bolling stages of cotton. During the two experimental years of 2018 and 2019, biochar application have significantly increased the soil organic carbon content of cotton and sugar beet at the seedling and harvesting stages by 0.98-13.2 and 0.66-12.1 g·kg^-1 if the differences of planting year and growth periods were not considered, respectively. Also, the increase rate was 1.20-7.43 at the cotton seedling stage and 0.66 to 13.2 g·kg^-1 at the harvest stage if the differences of planting year and crops were not considered, respectively, and was proportional to the application rates at the seedling stage. The emergence rate of cotton and sugar beet both increased with the increased soil bulk density, and increased first and then decreased with the increased soil temperature. The optimum temperature range for cotton and sugar beet germination was 22 to 26 ℃. The germination rate increased first and then decreased with the increased soil organic carbon contents, indicating that the excess increase of soil organic carbon content caused by high biochar application rates inhibited crop germination. When the application amount of biochar was 10 t·hm^-2, the seedling emergence rates of cotton and sugar beet were greater than 0.7, which was higher than that of the other three biochar application rates. However, when the biochar application rate was greater than 10 t·hm^-2, the emergence rates of cotton and sugar beet were lower than that of the treatment without biochar application. 【Conclusion】Therefore, a biochar application amount of 10 t·hm^-2 is recommended as the optimal amount for cotton and sugar beet field management considering its comprehensive effects on improving soil properties and crop germination rate.