Laying black plastic mulch over cabbage rows helps hold down weeds and keep moisture in the ground. It's a common trick even in a backyard garden. But when the harvest is done and you peel the plastic back, you find shreds of it lodged in the soil. The smallest bits never come up at all, and they stay behind in the bed.
Biodegradable mulch was developed to ease that problem. Microbes in the soil break it down over time, so it isn't supposed to leave behind the buildup of fragments that ordinary plastic does. A field study looking at how this material actually affects the soil out in the bed was published in an international journal in 2026.
Five kinds of biodegradable mulch on a cabbage bed
The research team laid five different mulches — each made from a blend of PBAT (polybutylene adipate-co-terephthalate) and PLA (polylactic acid) — across cabbage plots, and compared them against a plot with no mulch at all. Each product broke down and weathered at its own pace, yet over the cabbage's growing season the soil's physical and chemical properties, along with its overall function, stayed stable.
Yields shifted, too. Plots with biodegradable mulch produced roughly 2.6 to 7.6 percent more cabbage than the bare plot. In other words, over one season the mulch raised the harvest without harming the soil.
Bacteria and fungi responded differently
The effect of biodegradable mulch on soil microbes ran in opposite directions for bacteria and fungi. The fungal communities were more sensitive to which mulch was used than the bacterial ones were. Even among the same class of biodegradable material, the two communities behaved distinctly from one product to the next.
Nutrient-related measures in the soil — dissolved organic carbon, dissolved organic nitrogen, and microbial biomass nitrogen — emerged as the main drivers of the shifts in microbial communities. The direction of the fungi's response to nutrient limitation also varied with the mulch product. With some products, greater fungal diversity meant less nutrient limitation; with others, the pattern reversed. What came through clearly was that the soil's nutrient measures and the changes in fungal communities move together.
If you want to try biodegradable mulch in the garden
This study covers a single growing season. How nutrients and microbial communities would change after several years in the same bed is a question that needs more watching. Still, the finding that soil function held and yields rose over one season is reason enough to try it carefully in a home garden.
Start by laying it over just a row or two, and look at the soil yourself. After you've pulled the cabbage, the leftover broken-down material can feed nutrients back into the soil, so before you plant the next crop, check the soil's condition and work in some compost along with it.
Reference: Journal of Hazardous Materials 2026, field study of PBAT-PLA composite biodegradable mulch in cabbage cultivation
