Three-Year Field Experiment Shows Biodegradable Mulch Increases Vegetable Yield by 46%

China Science Daily reports that the "white pollution" caused by traditional plastic mulch film has long been a pain point for agricultural environmental protection. Biodegradable mulch film is regarded as an alternative solution. However, does it accelerate the decomposition of soil organic matter like traditional mulch film, thereby threatening soil health?

A three-year experiment conducted by a team from Bangor University in the UK on organic farms showed that biodegradable mulch films can increase vegetable yields by 43%-46%, without significantly altering soil organic matter content or harming soil bacterial diversity. Recently published in the Journal of the Science of Food and Agriculture, this study provides new evidence for the sustainable development of organic agriculture.

Yield "Counterattack": Biodegradable Mulch Increases Leek and Lettuce Production by Nearly 50%

The research team conducted a three-year field experiment on an organic farm in Wales, growing leeks, sweet corn, and lettuce to compare the effects of biodegradable mulch film with no mulch treatment. The results showed that the yields of all crops increased significantly: dry matter yield of leeks increased by 46%, sweet corn by 43%, and lettuce by 45%, while the yield of overwintering green manure also increased by 18%.

“This is equivalent to harvesting nearly half an acre more vegetables per acre of land,” explained the lead researcher. Biodegradable mulch film improves soil temperature and moisture, and reduces weed competition, allowing crops to thrive. Even more unexpectedly, the amount of crop residues and root biomass in mulched areas also increased, effectively “returning” more organic matter to the soil—the carbon input from sweet corn straw alone increased by about 50%.

Soil organic matter is "as stable as Mount Tai," while green manure compost is the true "carbon-enhancing hero."

Previously, there were concerns that biodegradable mulch films would accelerate the decomposition of soil organic matter (SOM) like traditional mulch films, leading to soil "thinning." However, experiments found no significant difference in SOM content between mulch-covered and no-mulch treatments over three years, with the organic matter proportion in the topsoil (0-10 cm) remaining stable at 12.6%-13.4%.

The organic input type that truly affects SOM is green manure compost, which increases SOM by 15% over three years, while there is no significant change in SOM for the poultry manure treatment group. This confirms that organic material input with a high carbon-to-nitrogen ratio is a key approach to maintaining the soil carbon pool. The synergistic application of PFM and compost not only supplements the soil's carbon source through compost but also enhances nutrient use efficiency with plastic film mulch, forming a virtuous cycle of "increasing yield and preserving soil."

Soil microorganisms remained "calm and undisturbed," with key microbial communities unaffected.

Soil bacteria are known as "ecosystem engineers" as they decompose organic matter and cycle nutrients. An experiment using 16S rRNA gene sequencing found that biodegradable mulching film had almost no effect on soil bacterial diversity: whether in overall diversity (Shannon index) or community structure (such as dominant bacterial groups like Acidobacteriota and Proteobacteria), there were no significant differences between mulching film-covered and non-mulching treatments.

The only minor change observed was a slight decrease in the number of Nitrospira (bacteria involved in nitrification) in the mulch-covered area, while the number of Pseudolabrys (associated with organic matter decomposition) slightly increased. However, these changes did not affect the overall function. The study suggests that the microbial community in healthy soil is "highly resilient," and the small amount of degradation products from biodegradable mulch did not disrupt its balance.

Organic Agriculture "Win-Win" Solution: Mulch Film + Green Manure Composting

Research indicates that the advantage of biodegradable mulch lies in "increasing yield without consuming land." Although it may accelerate the turnover of some easily decomposable organic matter, the residue return resulting from increased yield can "offset" this consumption. When combined with green manure compost, it can both leverage mulch to boost production and use compost to increase carbon, forming a "virtuous cycle."

Experts also caution that the experiment only lasted three years, and whether long-term use will affect the stable components of soil organic matter (such as humus) still needs to be observed. In the future, measures such as straw returning and crop rotation can be combined to make biodegradable mulch film a "green assistant" for organic agriculture.