The dual mechanisms of composite biochar and biofilm towards sustainable nutrient release control of phosphate fertilizer: Effect on phosphorus utilization and crop growth

The low utilization rate of phosphorus fertilizers is a common concern and is caused by high leaching loss rates and rapid nutrient release. While the precipitation with soil components also brings a series of problems. To address these problems, we propose a composite biochar and a hydrophobic biofilm to act as a synergistic mechanism for nutrient release control and to provide the required nutrients for crop growth. We optimized the preparation of composite biochar materials (1:1.2, 1.5 h, 450 °C) and explored the nutrient loading mechanism by different adsorption kinetic model fitting. The fitting curve showed that PO43− best fit with the Redlich-Peterson model with a high correlation coefficient (R2 = 0.9933). The water contact angle of a cotton stalk hydrophobic membrane material was 109°. Leaching experiments showed phosphate leaching losses increased with an increase in the amount in hydrophobic biofilm (2%, 4%, 6%), which showed a decreasing trend of 24%, 16% and 10%, respectively. After 31 d of nutrient release, the cumulative release rate of HCP2 was 65%, which matched the growth demand of corn maize crops and had a significant effect on early maize growth. All agronomic data showed optimized root length (32.5 cm), plant height (58.7 cm), dry weight (0.527 g) and fresh weight (4.907 g). This showed that the phosphate fertilizer carrier and co-release system constructed by the combination of biochar and biofilm has great advantages in promoting crop growth and a sustainable agricultural economy.