Abstract
This study aims to improve the slow-release performance of a film material for a controlled-release fertilizer (CRF) while enhancing its biodegradability. A water-based biodegradable polymer material doped with biochar (BC) was prepared from modified polyvinyl alcohol (PVA) with polyvinylpyrrolidone (PVP) and chitosan (CTS), hereinafter referred to as PVA/PVP-CTS(a)BC(b). An environmentally friendly novel controlled-release phosphate fertilizer (CRPF) was developed using PVA/PVP-CTS(8%)BC(7%) as the film. The effect of the PVA/PVP-CTS(8%)BC(7%) coating on the service life of the CRPF was investigated. The film was characterized via stress-strain testing, SEM, FTIR, XRD, and TGA analyses. The addition of the CTS modifier increased the stress of PVA/PVP-CTS(8%) by 7.6% compared with that of PVA/PVP owing to the decrease in the crystallinity of PVP/PVP-CTS(8%). The hydrophilic -OH groups were reduced due to the mixing of CTS and PVA/PVP. Meanwhile, the water resistance of the PVA/PVP-CTS(8%)BC(7%) was improved. And the controlled-release service life of the CRPF was prolonged. Moreover, the addition of BC increased the crystallinity of the PVA/PVP-CTS(8%) by 10%, reduced the fracture elongation of the material, and further improved the biodegradability of the PVA/PVP-CTS(8%)BC(7%). When the amount of BC added was 7%, the phosphorus release rate of the CRPF was 30% on the 28th day. Moreover, the degradation rate of the PVA/PVP-CTS(8%)BC(7%) polymer film was 35% after 120 days. This study provides basic data for applying water-based degradable polymer materials in CRFs.