A Degradable Mulch Film with Fertilizer Slow-Release Function Enhanced by Lignin

Mulch film and slow-release fertilizers are widely used in agriculture and horticulture, and it has become a trend to use degradable materials for the preparation of mulch films using slow-release materials. However, most degradable materials have poor performance or relatively high cost. In this study, three types of degradable materials, namely, poly(vinyl alcohol) (PVA), corn starch (CS), and alkali lignin (AL), were used as degradable materials to obtain a mulch film with a slow-release fertilizer function (MSRF). MSRF had excellent performance when 10% AL was added. The properties consisted of elongation at break (180.14%), water vapor permeability (203.8 g m–2 day–1), water resistance (its morphology remained good for 50 days), water absorption (300%), and urea release efficiency (cumulative release of 70.63% in 30 days). Rapid plant growth trials demonstrated that the MSRF had excellent functionality and that the MSRF could reduce the amount of fertilizer applied by about 70%. These excellent performances were due to the combination of chemical cross-linking (chemical bonding) between AL and PVA/CS molecular chains, the hydrogen bonding between the AL, PVA, and CS molecules, and the aggregation properties of AL. This provided a green and efficient strategy for the preparation and application of dual functions of mulching and the slow release of fertilizer.