Abstract
In this study, a novel type of slow-release fertilizer (SRF) was synthesized through lignin-based microcapsules. K2HPO4 and urea were coated by lignin and formaldehyde to prepare microcapsules of NPK compound SRF. The slow-release performance was measured by determining the NPK contents in water solution and soil column leaching. The release amounts of N, P and K after 5 days were 95.39, 95.28 and 96.75% in water, and 83.35, 96.62 and 90.75% in soil, respectively. The properties of SRF were analyzed by Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscopy. NPK release from the SRF was promoted by higher temperature and acid environment, but inhibited by alkaline environment. The first order kinetics equation provides the best correlation to describe nutrient release characteristics. The results indicated that SRF have good slow-release properties and are cost-saving and environment-friendly, and thus can efficiently improve the utilization efficiency of fertilizers in agricultural production.
Highlights
Due to the rapid growth of world population, modern agriculture plays a critical role in meeting the demand for foods and other agro-products.[1]
The remaining slow-release fertilizer (SRF) in the bottles was taken out every day, and dried at 100 °C to a constant weight to be weighed for calculating the cumulative release rate
After nutrient release (Figure 3c), the mass loss of SRF mainly occurred at the temperature ranging from 25 to 200 °C and 200 to 300 °C, which was induced by moisture loss and removal of light volatile components as well as the thermal decomposition of lignin
Summary
Due to the rapid growth of world population, modern agriculture plays a critical role in meeting the demand for foods and other agro-products.[1]. Wen et al.[11] reported the synthesis of a corncob-based semi-interpenetrating polymer network slow-release nitrogen fertilizer. Based on methylolated lignin and urea/hydroxymethylurea/urea-formaldehyde polymer, Jiao et al.[16] prepared a new type of slow-release threedimensional network polymer materials. These lignin-based SRFs are able to effectively increase urea-use efficiency, most of them only focus on urea as a nutrient for SRFs. to improve the utilization of multiple nutrients at the same time, it is important to prepare lignin-based slow-release compound fertilizers to reduce the frequency of fertilizer application. Based on the above studies of slow-release fertilizers, we prepared urea-formaldehyde resin microcapsules by an in situ polymerization method in this study. All the materials used were available from commercial sources and used as received
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