Rapid synthesis of a corncob-based semi-interpenetrating polymer network slow-release nitrogen fertilizer by microwave irradiation to control water and nutrient losses

This paper presents the rapid synthesis of a corncob-based semi-interpenetrating polymer network (semi-IPN) slow-release nitrogen fertilizer (SRFs) with bentonite additives via microwave irradiation at 320 W for 4.5 min. The SRFs were based on urea incorporated in a polymer matrix composed of corncob-g-poly(acrylic acid)/bentonite network and linear polyvinylpyrrolidone. The structure and properties of the sample were characterized. Swelling measurements and water-retention studies indicated that the water absorbency of the SRFs was 1156 g/g in distilled water and that the water-retention capacity of the soil with 2% SRFs was 20.3% after 30 days. In addition, the SRFs possessed lower N leaching loss amount (13.2%) and N migrate-to-surface loss amount (6.8%) compared with urea. The SRFs could effectively reduce the N release rate (56.6% of N was released after 30 days) and consequently facilitate the growth of cotton plants. Thus, the high-performance SRFs capable of controlling water and N losses could be widely applied to agricultural fields, and microwave irradiation could be a significant strategy to produce SRFs.