Biodegradable Plastic Mulch Films: Impacts on Soil Microbial Communities and Ecosystem Functions

Agricultural plastic mulch films are widely used in specialty crop production systems because of their agronomic benefits. Biodegradable plastic mulches (BDMs) offer an environmentally sustainable alternative to conventional polyethylene (PE) mulch. Unlike PE films, which need to be removed after use, BDMs are tilled into soil where they are expected to biodegrade. However, there remains considerable uncertainty about long-term impacts of BDM incorporation on soil ecosystems. BDMs potentially influence soil microbial communities in two ways: first, as a surface barrier prior to soil incorporation, indirectly affecting soil microclimate and atmosphere (similar to PE films) and second, after soil incorporation, as a direct input of physical fragments, which add carbon, microorganisms, additives, and adherent chemicals. This review summarizes the current literature on impacts of plastic mulches on soil biological and biogeochemical processes, with a special emphasis on BDMs. The combined findings indicated that when used as a surface barrier, plastic mulches altered soil microbial community composition and functioning via microclimate modification, though the nature of these alterations varied between studies. In addition, BDM incorporation into soil can result in enhanced microbial activity and enrichment of fungal taxa. This suggests that despite the fact that total carbon input from BDMs is minuscule, a stimulatory effect on microbial activity may ultimately affect soil organic matter dynamics. To address the current knowledge gaps, long term studies and a better understanding of impacts of BDMs on nutrient biogeochemistry are needed. These are critical to evaluating BDMs as they relate to soil health and agroecosystem sustainability

In vitro and in vivo antifungal activity of phosphite against Phytophthora parasitica in tomato

Phosphite is an alkaline salt of phosphorous acid. Its antifungal properties against some phytopathogenic fungi are increasingly valued in the context of a growing concern about the detrimental environmental effects of the standard biocides used to protect plants against pests and diseases. The purpose of this work was to analyze the in vitro and in vivo effect of phosphite in the development and evolution of Phytophthora parasitica on a tomato crop. The phosphite potential to limit and control the fungus growth was first established through an in vitro assay. In a second assay, in the greenhouse, tomato plants were transplanted into pots, in a substrate previously inoculated or not inoculated with the fungus mycelium. Inoculated and non-inoculated plants were sprayed with a range of phosphite concentrations (0, 0.9, 1.4, and 1.9 mg ml-1). The in vitro growth of the fungus mycelium was progressively restricted as phosphite concentration increased in the medium, and no fungus growth was detected with a phosphite concentration of 0.9 mg/ml. In the greenhouse assay, the development of the inoculated plants improved during the culture time when treated with phosphite, as was acknowledged by their higher chlorophyll content and by the values of stress indicators when compared with untreated plants. Moreover, the dry weight of the infected plants increased as the phosphite concentration was higher, and their maximum growth was obtained at 1.4 mg ml-1 phosphite. It is also noteworthy that, when compared to healthy plants, the infected plants increased their root to total weight ratio by 31.6% when treated with the highest phosphite concentration