Degradation mechanism for degradable color-matching mulch film and its effect on the yield of spring maize in Northeast China

Traditional polyethylene (PE) mulching (PM) films are difficult to degrade and recover in large-scale agricultural production. Fortunately, biodegradable, easily recyclable, and color color-matching mulching film (CM) can be expected for the agricultural sustainability and environmental protection. While current biodegradable mulching (DM) films are often costly to hinder their application. This research aimed to evaluate the degradation performance, mechanical properties, soil water-heat effects, and agricultural cleaning benefits (ACB) of CM, DM, and PM. Field experiments were conducted in Shenyang and Jianping, Liaoning Province, China. Three types of mulching films were selected as PM, DM, and CM. Among them, the CM consisted of a central black polyethylene (PE) strip that flanked by white biodegradable polybutylene adipate terephthalate (PBAT) strips. DM was made entirely of PBAT, while PM was conventional PE. A series of experiments were designed to determine the degradation rate, tensile strength, water-heat effects, crop yield, precipitation water use efficiency (PWUE), and ACB of the different mulching films. Soil temperature and moisture were measured using an ECH2O water temperature monitor. Degradation speed and mechanical strength were evaluated through visual grading and tensile tests, respectively. Field degradation rates were calculated using mass loss. The ACB was predicted to consider the purchase, recovery costs, and recovery rates. It was observed that the white PBAT sections of CM (CMW) was were degraded at a slower rate, compared with the DM, with a degradation rate of 77.48% after 120 days. This slight difference was attributed to the color differentiation. Specifically, the white PBAT sections were designed to degrade more slowly, in order to provide the initial soil warming, similar to the traditional PE films. The degradation rate of CMW was still substantially higher than that of PM, in order to avoid the soil pollution. The black PE section of CM (CMB) was maintained a significant portion of its initial tensile strength, with the remaining 81.74% after 105 days. This high tensile strength was allowed for easy recovery of CMB sections, thus ensuring that they were collected and disposed of properly. The combination of the biodegradable white PBAT sections and the recoverable black PE sections shared the more environmentally friendly CM, compared with the traditional PE and fully biodegradable films. In terms of soil temperature and moisture content, the CM performed exceptionally well during the early stages of coverage. The highest CM temperature increased by 1.23°C, and the moisture content increased by 25.20%, compared with the DM. The optimal soil conditions were then provided for the seed germination, root growth, and nutrient uptake in the crop growth and development. There were the similar soil temperatures and moisture retention of CM and PM, indicating the promising sustainable alternative to traditional mulching films. The economic analysis revealed that the CM saved 43.51 yuan per mu, compared with the DM, whereas, the CM increased costs by 12 yuan per mu, compared with PM. These cost savings were attributed to the reduced need for the film recovery and disposal, as well as the increased crop yield and PWUE associated with CM. The recovery rate of CMB was 82.31% similar to PM, fully meeting the requirement for over 85% residual film recovery. As such, the CMB sections were properly collected and disposed of to minimize the soil pollution. The ACB of CMB was also similar to the PM. The CM can be expected to provide the similar benefits, in terms of soil health and crop productivity as traditional PE films, while also reducing environmental pollution. Therefore, the CM can also serve as the a promising solution to the sustainable agriculture and environmental protection. In conclusion, the colored biodegradable CM was combined with the excellent properties of the traditional PM and DM. Black The black PE strip of CM was used to ensure the high tensile strength for easy recovery, while the white PBAT strip was to degrade effectively, thus reducing soil pollution. The comparable crop yields and superior WUE were achieved in the CM, indicating the more cost-effective and environmentally friendly than DM. Therefore, the CM can also offer the a promising solution to the sustainable agricultural production and environmental protection.