An antibacterial mulch film is required for the rapid response to two key meteorological factors (temperature and humidity) in crop diseases during agricultural production. Conventional disease prevention and control measures respond to the dynamic meteorological conditions—for instance, when a sudden rise in field temperature or a surge in humidity can trigger an outbreak of diseases, often fail to adjust prevention and control strategies in a timely manner; Prevention and control can rely mainly on the large-scale pesticide spraying. This "flood-irrigation" style of pesticide application can easily result in low pesticide utilization efficiency, i.e., substantial pesticide loss. In turn, a series of environmental issues can also cause problems, such as soil pollution and water eutrophication. Meanwhile, excessive pesticide residues in agricultural products can also pose a dual threat to the ecological environment and human health. In this study, an antibacterial mulch film with temperature and humidity responsiveness (CW-C-Gel-WFM) was successfully developed using carnauba wax, gelatin, and temperature-sensitive straw fibers as core raw materials. Each component of mulch film also shares the structural functions. Among them, carnauba wax and gelatin acted as temperature-controlled release materials. Their own structural states were adjusted at the environmental temperature, thereby regulating the pesticide release rate; While temperature-sensitive straw fibers served as carriers, due to their unique porous fiber structure. The active ingredients of pesticides were stably loaded in environmental humidity, thus synergistically achieving precise regulation of "on-demand release". The mulch film was synergistically adjusted as the timing of pesticide release using the physical barrier of carnauba wax and the temperature-sensitive responsiveness of gelatin. As such, the pesticide-controlled release was realized with the changes in field temperature and humidity. Pesticide loss caused by blind release was effectively reduced to dynamically optimize the field pesticide concentration, according to the disease risk at different stages of crop growth, significantly enhancing the controllability of the crop growth environment. Furthermore, the thickness of the mulch film's barrier layer had a significant impact on the mechanical properties (e.g., tensile strength and elongation at break) of CW-C-Gel-WFM. The tensile strength of the mulch film showed a trend of firstly decreasing, then increasing, and finally decreasing again, as the thickness of the barrier layer increased. While the elongation at break decreased slightly. The performance of the straw-fiber-based mulch film was attributed to the repeated coating with a coater and the interaction arising from carnauba wax molecules filling the gaps between gelatin molecules. The tests further indicated that the air permeability rate of the mulch film decreased significantly with the increasing thickness of the barrier layer—when the thickness of the barrier layer reached 30 μm, the air permeability rate dropped to 12.03 μm/(Pa·s). The water evaporation was effectively reduced in the area covered by the mulch film. At the same time, the stable soil humidity was maintained to avoid the excessive volatilization of pesticides caused by overly strong air permeability. In addition, the moisture absorption performance of CW-C-Gel-WFM was significantly superior to that of the control mulch film without carnauba wax (C-Gel-WFM), due to the hydrophobicity of the carnauba wax coating. The mulch film from structural collapse was also prevented under excessive moisture absorption, in order to avoid the premature degradation of pesticides caused by excessive contact with water. Pesticide release kinetics analysis was carried out to evaluate the performance of controlled-release mulch films. The results showed that the pesticide release rate slowed down significantly at constant temperature, with the increasing thickness of the carnauba wax barrier layer, and the controlled release time was extended accordingly. When the thickness of the barrier layer reached 30 μm, the maximum controlled release time reached 96, 120, and 168 h, respectively, which was 48-60 h longer than that of C-Gel-WFM. More importantly, the temperature dominated the pesticide release, with 40 ℃ as a critical threshold: Once the environmental temperature was higher than 40 ℃, pesticide release mainly followed the Fickian diffusion—at this time, the high temperature intensified the molecular movement of the carnauba wax barrier layer for the more internal pores. As such, the pesticides were mainly released from the polymer matrix through molecular diffusion; Once the temperature was lower than 40 °C, the pesticide release shifted to the non-Fickian diffusion. The release was controlled by the swelling of gelatin, the relaxation of polymer chains, and the physical diffusion of carbendazim. The mulch film can be expected to flexibly adjust the release mode according to different temperature environments, further improving the precision of pesticide use. The pot experiments and soil microbial analysis also demonstrated that CW-C-Gel-WFM shared a controlled bacteriostatic behavior to promote plant growth.

Mulching as a traditional field management technique, boasts the benefits of improving soil ecology and maintaining soil temperature and moisture. The biodegradable plant fiber mulch produced from crop straw boasts abundant raw material sources and has similar temperature and moisture retention effects to plastic mulch, which would have no phenomenon of soil hardening, and compromised crop cultivation and sowing quality. The quality of straw fiber obtained through physical methods cannot meet the demand of mulch film. To improve the mechanical properties of straw fiber mulch film and reduce pulping time, this study introduces a method of preparing straw fiber mulch raw materials through biological pretreatment combined with extrusion-explosion. To explore the optimal combination of process parameters for this technology, three-factor and five-level quadratic orthogonal central composite rotatable design experimental approach was employed, with pretreatment time, spindle speed, and Clearance of mould head selected as the experimental factors, and tensile index, pulping time, and fiber aspect ratio as performance indicators. The results showed that pretreatment time and spindle speed, spindle speed and clearance of mould head had very significant effects on the tensile index (P<0.01). Pretreatment time and clearance of mould head have significant effect on tensile index (P<0.05). Pretreatment time and spindle speed, pretreatment time and clearance of mould head have significant effect on pulping time (P<0.05). Spindle speed and pretreatment time had very significant effect (P<0.01) on pulping time, the spindle speed and clearance of mould head has no significant effect on fiber aspect ratio (P>0.05). Pretreatment time and spindle speed have very significant effect on fiber aspect ratio (P<0.01). Pretreatment time and clearance of mould head have significant effect on fiber aspect ratio (P<0.05). The optimal combination of process parameters was determined to be 10 days of pretreatment, a spindle speed of 120 r/min, and a Clearance of mould head of 3 mm. The resulting fiber mulch exhibited a tensile index of 9.57 N·m/g, a pulping time of 81.4 minutes, and a fiber aspect ratio of 10.97, with a relative error not exceeding 5% compared to the theoretical optimal values. The rice straw fiber-based mulch prepared under these conditions meets the technical requirements for crop cultivation in both irrigated and dry fields. This study provides a basis and technical support for the production of fully biodegradable plant fiber mulch film from rice straw.

Appropriate mechanized straw returning and tillage sowing techniques were effective means to optimize soil physical properties and enhance agricultural productivity, as well as important measures for the conservation and restoration of mollisols region in Northeast China. Under the condition of full-scale maize straw returning, four mechanized tillage and sowing modes were set, including plough tillage and sowing (PTS), combined tillage and sowing (CTS), no-tillage and sowing (NTS), and no-tillage and sowing with straw mulching (NTSM). In 2020 and 2021, the study investigated the effects of different mechanized tillage and sowing modes on soil physical properties, soybean yield and economic benefits. The results showed that during the pod-setting and pod-filling period of soybean, the NTS and NTSM treatments exhibited better effects on deep soil insulation and shallow soil moisture retention, the soil physical structure of PTS and CTS treatments were relatively ideal. Compared with PTS and CTS treatments, NTS and NTSM treatments significantly increased soil gravimetric water content (SWC) by 2.35% to 7.98% in the 5-15 cm soil layer and increased soil temperature (ST) by 3.94% to 10.42% in the 25-35 cm soil layer (p<0.05), significantly increased soil bulk density (SBD) by 2.98% to 6.72% and significantly reduced soil total porosity (STP) by 3.88% to 6.53% in the 5-25 cm soil layer, and significantly reduced soil gas phase ratio by 8.26% to 6.27% at the 15-25 cm soil layers, which caused soil three-phase ratio (STPR) of PTS and CTS treatment in 15-25 cm soil layer were relatively ideal. The soybean yield of NTSM treatment in 2020 was not significantly different from PTS and CTS treatment (p>0.05), the soybean yield of NTSM treatment in 2021 significantly increased by 7.30% and 5.84% over PTS and CTS treatments, respectively. And the average annual profit per unit area of NTSM treatment increased by 12.84%, 12.41% and 8.57% compared with PTS, CTS and NTS treatments, respectively. Therefore, it was recommended to combine NTSM technique with PTS or CTS technique in a maize-soybean rotation system in mollisols region. The research results provided reference for the selection of appropriate mechanized tillage and sowing techniques in Northeast China’s mollisols region and had important guiding significance and practical value for the construction of rational plow layers and the implementation of conservation tillage.