Effects of biochar on soil properties and agricultural runoff nutrients in new cultivated farmland in the Yellow River Basin

[Objective] Biochar was used as a soil conditioner to analyze the effects of biochar on soil moisture, conductivity and nutrients in new cultivated land and agricultural runoff nutrients in the Yellow River Basin. [Methods] In Caoxian County, Heze City, Shandong Province, a field experiment was conducted with rice as the test crop, and the biochar application rates were set at 0 t/hm2 (CK), 4.5 t/hm2 (C1), 9 t/hm2 (C2) and 13.5 t/hm2 (C3) treatments were used to determine soil water content, electrical conductivity, soil nutrients and agricultural runoff nutrients under different treatments, and to analyze the effects of biochar on rice yield, as well as its correlation with soil physicochemical properties and agricultural runoff nutrients. [Results] Compared with the control, the application of biochar had a significant effect on soil water content, and the increase of soil volume water content decreased with the increase of biochar application amount. In August and September, the soil conductivity treated by C1 and C2 was significantly higher than CK, and there was no significant difference in the rest of the rice growth period. The application of biochar could promote the absorption and utilization of soil nutrients, but had no significant effect on soil pH. C1 and C2 treatments generally increased the nutrient content of farmland regression water, and C3 treatments generally reduced the nutrient content of farmland regression water. The application of biochar could increase the yield of rice, especially the C2 treatment, which was 8.49%. The correlation analysis showed that soil total phosphorus, total potassium and available phosphorus were significantly positively correlated with rice yield, and soil nitrate nitrogen and SO2- 4 contents were significantly negatively correlated with rice yield. The total nitrogen, total potassium and nitrate nitrogen in agricultural runoff were significantly positively correlated with rice yield. [Conclusion] The application of biochar can increase soil moisture, affect soil nutrients and electrical conductivity, and help to increase nutrient content in new created cropland in the Yellow River basin, and can be used as a soil amendment for new created cropland in the Yellow River basin. The recommended application amount is 9 t/hm2.