Optimization of manufacturing parameters for sterilizing functional straw fiber mulch

At present, amount of pesticides used in agricultural production in China is relatively large, and the application method is not scientific enough, which brings about problems such as increased agricultural production costs, excessive pesticide residue in agricultural products, and environmental pollution. Pesticide controlled release technology is an effective method to improve pesticides utilization efficiency, reduce the amount of pesticides use, and reduce environmental pollution. The straw fiber based film is a fully degradable mulch film made from crop straw as raw material. It has the functions of increasing soil temperature, preserving soil moisture, inhibiting grass, protecting fertilizer and controlling soil erosion during the cultivation process. If the straw fiber based film is used as a carrier to load the pesticide and form the sterilizing functional mulch, the stability and effective period of the pesticides can be improved because the straw fiber base film is protected from light. In this study broad-spectrum fungicide carbendazim was mixed with chitosan, which work as adhesive, at normal temperature and coated on the rice straw fiber film. To improve the sustained release effect and the effective utilization rate of carbendazim pesticide, the manufacturing parameters of the sterilizing functional mulch were optimized by applying the four factors and five levels quadratic regression orthogonal rotation center combined experimental method. Using the wood pulp fibers to build skeleton and adding rice straw fiber as the main filling material, through pre-experiment and reference, the wet strength agent, sizing agent, adhesive concentration and the coating thickness were selected as influencing factors, and the dry tensile strength, wet tensile strength, air permeability, degradation cycle, and effective utilization rate of pesticides were selected as the performance evaluation indexes. Under the performance evaluation indexes of the dry tensile strength ≥ 35 N, the wet tensile strength ≥ 15 N, the air permeability ≤ 2 µm/Pa•s, the degradation cycle ≥ 60 d, the effective utilization rate of pesticide ≥ 80%. The optimized factors range is determined as follow: wet strength agent addition of 0.8% to 0.9%, sizing agent addition of 0.5% to 0.7%, adhesive concentration of 2.0%, and coating thickness of 20 µm. The results showed that the adhesive concentration and coating thickness could change the morphology of the straw fiber based film and affect inter-fiber force, thereby change the dry tensile strength, the wet tensile strength, the air permeability, and the degradation cycle of the straw fiber base film. Compared to straw fiber based film, the sterilizing functional straw fiber mulch not only improved the dry tensile strength and the wet tensile strength, but also reduced the air permeability and prolonged the degradation cycle. And the most important thing was the sterilizing functional straw fiber increased a new function which could sterilize innovatively. And the sterilizing functional straw fiber mulch provides a functional trend for the straw fiber mulch and provides a reference to improve pesticides utilization efficiency and reduce the amount of pesticides use of broad-spectrum fungicide carbendazim. Our study also provides a reference for the research and development of broad-spectrum sterilizing functional straw fiber mulch.