A three-year field trial in the UK shows that biodegradable mulch increases vegetable yields by 46% without damaging soil health
The "white pollution" caused by traditional plastic mulch has long been a sore point in agricultural environmental protection, and biodegradable mulch is considered an alternative. But does it accelerate the decomposition of soil organic matter like traditional mulch, threatening soil health?
A three-year experiment conducted by a team from Bangor University in the UK on an organic farm showed that biodegradable mulch can increase vegetable yields by 43%-46% without significantly altering soil organic matter content or compromising soil bacterial diversity. This study, recently published in the Journal of the Science of Food and Agriculture, provides new evidence for the sustainable development of organic agriculture.
Yield "Rebound": Biodegradable mulch increases leek and lettuce yields by nearly 50%.
The research team conducted a three-year field trial on an organic farm in Wales, growing leeks, sweet corn, and lettuce, comparing the effects of biodegradable mulch with no mulch treatment. The results showed significant yield increases for all crops: dry matter yield of leeks increased by 46%, sweet corn by 43%, lettuce by 45%, and even winter green manure yield increased by 18%.
"This is equivalent to harvesting nearly half an extra acre of vegetables per acre of land," explained the research leader. Biodegradable mulch improves soil temperature and moisture and reduces weed competition, allowing crops to thrive. Even more surprising, crop residue and root biomass also increased in the mulch-covered areas, effectively returning more organic matter to the soil-carbon input from sweet corn stalks alone increased by approximately 50%.
Soil organic matter is as stable as a rock, and green manure compost is the true carbon enhancer.
Previously, concerns were raised that biodegradable mulch, like traditional mulch, would accelerate soil organic matter (SOM) decomposition and lead to soil thinning. However, the experiment found no significant difference in SOM content between mulch-covered and unmulch-covered treatments over three years. The organic matter content in the topsoil (0-10 cm) remained stable at 12.6%-13.4%.
The true impact on SOM was the type of organic input: green manure compost increased SOM by 15% over three years, while there was no significant change in SOM in the poultry manure treatment group. This confirms that the input of organic materials with a high carbon-to-nitrogen ratio is a key pathway for maintaining soil carbon. The synergistic application of PFM and compost not only replenishes soil carbon through compost but also improves nutrient utilization efficiency through mulch application, creating a virtuous cycle of increasing production and nourishing the soil.
Soil microbes remain stable, with key bacterial communities undisturbed.
Soil bacteria, known as "ecosystem engineers," decompose organic matter and recycle nutrients. Experimental 16S rRNA gene sequencing revealed that biodegradable mulch has little effect on soil bacterial diversity: neither overall diversity (Shannon index) nor community structure (e.g., dominant bacterial groups such as Acidobacteriota and Proteobacteria) differed significantly between mulch-covered and unmulch-covered treatments.
The only minor changes were a slight decrease in the abundance of Nitrospira (bacteria involved in nitrification) and a slight increase in Pseudolabrys (associated with organic matter decomposition) in the mulch-covered areas, but these changes did not affect overall soil function. The study speculates that the microbial community in healthy soil is resilient, and the small amount of degradation products from the biodegradable mulch does not disrupt its balance.
A "Win-Win" Solution for Organic Agriculture: Mulch Film + Green Manure Compost
Research indicates that the advantage of biodegradable mulch film is that it "increases yield without consuming land." While it may accelerate the turnover of some easily degradable organic matter, the resulting residue return from increased yields can offset this loss. Combined with green manure compost, the mulch film can both increase yields and increase carbon dioxide emissions, creating a "virtuous cycle."
However, experts caution that the experiment only lasted three years, and whether long-term use will affect stable components of soil organic matter (such as humus) remains to be seen. In the future, biodegradable mulch film could be combined with measures such as returning straw to the fields and crop rotation to make it a "green companion" to organic agriculture.
