Liu Fei, Wang Ting, Bai Yujia, Tian Yibo, Zhang Jing, Meng Huaju
Response surface methodology was used to analyze the effects of molding temperature, pressure, proportion of binder and mixing ratio of raw materials on the density of seedling bowl, breakage by dropping, and breakage by pressure. Then the process parameters were optimized by applying the satisfaction function method and multi-population genetic algorithm. In addition, the effect of seedling bowls on the physicochemical properties of soil was also analyzed. The results showed that the density, drop breakage rate and compressive breakage rate of seedling bowls reached 0.908 g/cm3, 2.98% and 2.68%, with the temperature of 60-110 ℃, pressure of 8-18 MPa, binder to raw material mass ratio of 0.6∶1-1.3∶1, and the corn stover charcoal content of 10%-60%. The optimal combinations of process parameters were temperature 67 ℃, pressure 13.64 MPa, binder to raw material mass ratio 0.78∶1, and corn stover charcoal to Sophora japonica raw material mass ratio 3∶7, under which the density, drop breakage rate and compressive breakage rate of seedling bowls were 1.032 g/cm3, 2.65% and 2.34%, which were only 0.02%, 0.01%, and 0.03% from the predicted values. After the seedling bowls were buried in the soil for 8 weeks, the soil pH value decreased from 8.92 to 8.02, and the soil quick-acting nitrogen, quick-acting phosphorus, and quick-acting potassium increased by 57.1, 27.0, and 38.0 mg/kg respectively, which indicated that the corn stover charcoal-mixed Sophora japonica biomass seedling bowl could effectively reduce the soil pH value and improve the soil fertility.