Biodegradable Carboxymethyl Chitosan/Polyvinyl Alcohol Hymexazol-Loaded Mulch Film for Soybean Root Rot Control

Soybean root rot is an important disease that has affected soybean crops in recent years, but the available control methods still do not provide good protection for soybeans. In this study, three biodegradable mulch films (HML@CMCS, HML@PVA, HML@CMCS/PVA) were prepared from carboxymethyl chitosan (CMCS) and polyvinyl alcohol (PVA), and hymexazol (HML) was loaded on them. The surface and cryofractured surface were compared via micromorphological observations using SEM, AFM, and 3D measurements. Mechanical, water barrier, and optical properties were compared between the different films, and the results showed that the composite film (HML@CMCS/PVA) had better tensile properties, lower water content (35%), and lower water solubility (28%), while water barrier properties were significantly improved. HML@CMCS/PVA also had better light transmission than commercial films (opacity at 600 nm of 1.92). Finally, the composite film was selected to study antifungal properties, soil degradability, and biosafety. The results showed that it exhibited significant inhibitory activity against Fusarium oxysporum and could effectively control soybean root rot, while degradation reached 58% after 7 d of soil burial, and the mortality of earthworms relative to the microplastics produced by the film within 7 d (23.33%) was much lower than that of the commercial film, demonstrating its excellent biosafety. This study provides a new approach for the on-farm management of soybean root rot and the reduction in soil microplastic pollution

Diversity Temporal–Spatial Dynamics of Potato Rhizosphere Ciliates and Contribution to Nitrogen- and Carbon-Derived Nutrition in North-East China

Ciliates are an important component of the rhizosphere microorganism community, but their nutritional contribution to plants has not been fully revealed. In this paper, we investigated the rhizosphere ciliate community of potatoes during six growth stages, illustrated the spatial–temporal dynamics of composition and diversity, and analyzed the correlation between soil physicochemical properties. The contributions of ciliates to the carbon- and nitrogen-derived nutrition of potatoes were calculated. Fifteen species of ciliates were identified, with higher diversity in the top soil, which increased as the potatoes grew, while they were more abundant in the deep soil, and the number decreased as the potatoes grew. The highest number of species of ciliates appeared in July (seedling stage). Among the five core species of ciliates, Colpoda sp. was the dominant species in all six growth stages. Multiple physicochemical properties affected the rhizosphere ciliate community, with ammonium nitrogen (NH4+-N) and the soil water content (SWC) greatly influencing ciliate abundance. The key correlation factors of ciliates diversity were NH4+-N, available phosphorus (AP), and soil organic matter (SOM). The annual average contribution rates of carbon and nitrogen by rhizosphere ciliates to potatoes were 30.57% and 23.31%, respectively, with the highest C/N contribution rates reaching 94.36% and 72.29% in the seedling stage. This study established a method for estimating the contributions of carbon and nitrogen by ciliates to crops and found that ciliates could be potential organic fertilizer organisms. These results might be used to improve water and nitrogen management in potato cultivation and promote ecological agriculture