Characterization, swelling and slow-release properties of a new controlled release fertilizer based on wheat straw cellulose hydrogel

• The hydrogel containing fertilizers (N and P) was based on wheat straw.
• Effects of various conditions on the properties of hydrogel were investigated.
• The fertilizer diffusion coefficients were evaluated by a kinetic equation.
• The hydrogel used in agriculture can provide both water and fertilizer to plants.

A novel wheat straw based semi-interpenetrating polymer networks (semi-IPNs) hydrogel with slow-release fertilizers of nitrogen and phosphorus was prepared by the method of solution polymerization. The influences of particle sizes, salt solutions, ionic strength and pH changes on the swelling and fertilizer releasing properties of the product were investigated. Effect of cations on both swelling and fertilizer release properties were observed in the order of Na+ > K+ > Ca2+. The product could hold more water in the pH range of 6–9. The swelling behaviors of the product in various salt solutions, ionic strength and pHs conditions were evaluated by Schott's second-order swelling kinetics model. The fertilizers diffusion parameters of the product could be assessed by a cubic form perfectly according to the diffusion coefficients in the kinetic equation.

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