Preparation and properties of functional materials of montmorillonite-biochar composite slow-release fertilizer

Biochar was prepared from corn straw, and the basic properties of biochar were studied, including elemental analysis, surface functional groups, and crystal structure. The soil leaching experiment of compound fertilizer was carried out by mixing three substances of biochar, montmorillonite and urea in different proportions to form a composite fertilizer, and the cumulative release rate of nitrogen in the soil of the composite material was investigated. In the soil leaching experiment, after 18 days of leaching, the cumulative release rate of nitrogen at biochar: urea was 1:1, which was 17.9% lower than that of pure urea, the quasi-first-order kinetics could better fit the process, and the release rate constant was 0.233 min^-1 ; when the Montmorillonite: urea is 1:1, the nitrogen release after filtration is 16.4% lower than that of pure urea at 18 days, and the release process is in line with the secondary kinetics, and the rate constant is 3.63×10-3%·min^-1. When montmorillonite: biochar:urea=1:1:1, the sustained release performance of the compound fertilizer was optimal, and the cumulative release rate of nitrogen at 18 days was 56.2%. The results show that the compound fertilizer formed by biochar, urea and montmorillonite granulation can better delay the release of urea.