The Effects of Biochar-Based Organic Fertilizer and Mineral Fertilizer on Soil Quality, Beet Yield, and Sugar Yield

The addition of biochar-based organic fertilizer (BOF) can improve sugar beet yield, but its effects on the growth of sugar beet and on soil quality at different densities remain unclear. Six treatments, comprising two densities D1 and D2 (80,000 and 90,000 plant ha-1) and three application rates B1, B2, and B3 (2.75, 3.25, and 3.75 t ha-1) of BOFs + mineral fertilizer, respectively, are investigated in this research. The mineral fertilizers are typically used to supplement the total N, P2O5, and K2O deficiencies. The BOFs were used in the soil before sowing, and the mineral fertilizer was added to the soil after the first pair of true leaves was grown. At 160 days after sowing (DAS), the root-to-shoot ratio under the D2B2 treatment was significantly higher than that under the other treatments. The effect of density on the photosynthesis rate of sugar beet was not significant. The BOF application amount and density exerted interaction effects on soil physicochemical properties and the activities of different soil enzymes affecting each other. Both the D2B2 and D2B3 treatments reduced the content of NO3--N in the 40-60 cm soil layer. Combined 90,000 plants ha-1 with 3.25 t ha-1 BOFs can increase the soil nutrient content of the 0-60 cm soil layer, improve the rhizosphere soil environment, promote the uniform distribution of dry matter, and increase sugar production.