Exploring alternatives to plastic mulch

Author: Natalie Hoidal, UMN Extension Educator, local foods and vegetable crops
Originally published in 2021; updated in 2026

There are so many benefits to using plastic mulch including moisture retention, weed control, and soil warming, but the environmental impact is hard to ignore. It's estimated that in the US alone, farmers use around 1 billion pounds of plastic annually. In this article, I'll review some alternatives and share up-to-date research and grower feedback. 

Plastic is a mainstay on most vegetable farms,
but farmers are working hard to find good alternatives.
Photo NH

 

Alternative plastic mulch-like products

1. Biodegradable plastic mulch

If a grower wanted to swap black plastic mulch with something nearly identical, but more environmentally friendly, biodegradable plastic mulch may be the best option. These plastics perform similarly to regular plastic mulch, but rather than removing your mulch at the end of the season, it's tilled into the soil where it decomposes. They are generally made of vegetable starches and plant-derived polymers.

Many growers have questions about the soil health impacts of biodegradable mulches. Unfortunately at this point, the research is fairly unclear. Some studies show impacts to soil microbial communities, and others do not. There is also substantial variation between products. Overall, biodegradable mulch impacts the soil in two ways. 1. Just like regular plastic mulch, covering the soil surface with a relatively impermeable black plastic changes the dynamics of the soil underneath by reducing light infiltration, increasing heat, trapping moisture, and reducing water infiltration, evaporation, and gas exchange. All of these changes impact microbial communities, root development, and nitrogen use efficiency. Impacts vary depending on the soil conditions and climate in which mulches are used. In cool climates, plastic mulches may increase microbial activity by warming the soil, whereas in warm climates, mulches may warm the soil beyond the optimal temperature range for many microbes. In general, the use of plastic mulches increases nitrogen use efficiency (Bandopadhyay et al., 2018). 2. Following incorporation, biodegradable mulches add carbon, microorganisms, and other materials such as adherent chemicals and dyes. While the breakdown products of biodegradable mulches are generally considered non-toxic, there is limited research on the long-term effects of using these materials. 

Since no current models of biodegradable mulch meet the criteria of the national organic program, these mulches can only be used in organic fields if they are removed at the end of the season (at which point they are often already starting to decompose, which results in a lot of extra labor and annoyance). 

One of the main reasons growers have not quickly adopted the use of biodegradable mulch is that it can be quite messy when it begins to degrade, and pieces can stick to produce, especially produce that touches the ground such as melons. For growers who have customers on-site, the small pieces of black plastic scattered around the farm may be considered unsightly. 

It is worth noting that some initial research suggests that after tilling biomulch into the soil, the decomposition process may tie up nitrogen in the soil for a period of weeks (just like you would expect after cover crops, or after adding any carbon-based material to the soil). As such, it is advisable to avoid planting a second crop immediately after tilling your mulch under (just like you would wait a few weeks to plant after you've terminated a cover crop). 

Penn State Extension educators published a series of case studies with grower reviews and tips for using biodegradable plastic mulch. 

There are a wide array of biodegradable mulches on the market, 
and all perform a bit differently. Researchers in multiple states are actively
trialing biomulches to compare their efficacy and assess soil impacts. 
Image from the Wortman research lab in Nebraska. 

2. Paper mulch

Paper mulches are made of cellulose-based materials. They can be applied using the same methods (i.e. mulch layers), but many growers find that the edges are more likely to tear during application if the disks are not set up at the right angle. Some researchers have opted to install paper mulch by hand due to the degree of tearing. Others recommend re-burying the edges at least once or twice during the season, as loose edges can catch in the wind or on equipment and tear. There are newer products with "creped paper" that generally work better with mulch laying equipment than the basic, flat paper mulch. Paper mulch can be disked into the soil at the end of the growing season. 

Paper mulches also tend to develop more tears and holes throughout the season than standard plastic mulch. There seem to be fewer studies on paper mulch than on other biodegradable mulches, but many show that it keeps soil consistently cooler than plastic mulch. This is likely in part due to the lighter color of plastic mulches, which tend to be tan to brown, but there are newer black paper mulches entering the market. As such, if you're considering trying paper mulch, try it first on cooler season crops. 

2021 trials in Morris MN compared paper, plastic, and biodegradable mulch on outdoor strawberries and high tunnel peppers. The paper mulch performed about as well as the plastic mulch from a weed control perspective. Strawberry yields were the same, but high tunnel peppers yields were a bit lower. You can read more about that trial here. 

Paper mulch. Image: Johnnys

3. Developments in new technologies

Researchers in Morris were working on a bio-based spray-on mulch made from agricultural residues, but the trials ended when staff left. The spray-on mulches had some promise, but did not perform as well as standard plastic, biodegradable plastic, and paper mulches. 

Organic mulches

1. Straw

Straw is one of the most universally-used organic mulches, and for good reason. It achieves many of the same benefits as plastic mulch: weed suppression, reducing fertilizer leaching, and moisture retention. It also helps to reduce the incidence of splash-dispersed pathogens, and initial research shows that it can help to reduce Alternaria pressure in Brassicas. Straw mulch has also been cited as an Integrated Pest Management strategy for some pests including onion thrips and potato beetles, because it can interfere with pupation, and can support communities of beneficial insects. 

Straw does keep the soil cool, which for some crops, can have negative yield impacts (but for cool season crops is ideal). Fields mulched with straw can also cause problems in squash and pumpkins if a fall frost occurs; we tend to see more damage in straw mulched plots than bare soil. 

Make sure to purchase high quality, weed free straw, or you may end up with more weeds than you started with. Unfortunately, even straw labeled as "weed free" very often comes with weeds, or with viable seeds. I've used straw mulch for years and every year I end up with a lot more wheat or rye than I'd like. I've also seen a few cases where growers have spread straw over large areas on farms, and then the straw germinated, creating a wheat field in what should have been a pepper field. So, this is always a risk! Make sure you know your supplier and you know about their practices before using straw on a large scale. 

Many growers prefer to run at least one cultivation pass before mulching to eliminate the first flush of weeds before laying the straw. 

Sprouting hay bale / a reminder to purchase
weed free, high quality straw. Photo NH

2. Strip tilling or direct seeding into a rolled cover crop 

We're seeing more and more vegetable growers experimenting with strip tilling, or direct planting into a field of rolled winter rye. There's still a lot to figure out in these systems, but they are promising for a few main reasons. 1. Rather than importing straw and spreading it, you're essentially creating straw in place with a cover crop. 2. With this system, you're also able to keep living roots in the soil over the winter. Dr. Ajay Nair's team is leading a lot of this research in Iowa, and you can read more about some of their trials here. In Minnesota, rolling and crimping a winter cereal often does not successfully terminate it. If conditions are too wet, rolling and crimping may not be sufficient to break the stems, and instead may simply push them over. Some growers who use this system first terminate their cover crop with an herbicide or by mowing it. If you're going to mow rye or wheat, it has to happen at flowering. If it happens earlier, the cover crop will re-grow. Some years this happens in early June, and other years it happens later in June. So, if you're planning to mow your cover crop, make sure you're following it with a crop that can be planted late (e.g. a pumpkin or squash that matures quickly, a half season Brassica crop). Transplanting pumpkins and squash can also help to alleviate the challenge of planting a bit late. In general, mowing a winter rye or wheat cover crop works best with a basic sickle-bar mower. The residue tends to clog flail mowers.

There are pumpkin growers who direct seed into mowed or rolled rye - this works best for larger seeded crops. For smaller seeded crops, strip tillage, the practice of tilling the strips where you want to plant and leaving the rows in between untilled, is a good compromise. Read more about strip till trials from Dr. Nair's lab in the link above. Keep in mind that soil covered in straw does not get as warm as soils covered in plastic; using row cover early in the year can help offset the cooler temperatures. 

Farmers seeding pumpkins into a 
terminated rye cover crop. In this case there was limited
rye establishment, so the weed control benefit was limited
Photo: Annie Klodd

3. Deep compost mulch

Deep compost mulching is simply the practice of adding a thick layer weed-free compost on top of your soil, essentially burying weed seeds. Depending on how much compost you're able to generate on-site, this system can be prohibitively expensive. This can work well for farmers who connect with local schools, hospitals, or other institutions who compost large quantities of food-waste. Keep in mind that it is possible to add too much compost, especially if it is high in phosphorous. We often see sky high phosphorus levels and imbalanced soil chemistry in fields with deep compost mulch. Test your soil regularly to make sure you're not over-applying certain nutrients. The other negative dynamic we see in these systems is that a heavy layer of compost over the soil can dry out easily and become hydrophobic, which causes issues with watering all season long. Finally, in some systems with extremely high organic matter (>8%), we can start to see more root rot pathogens that thrive in decomposing organic matter.

4. Woodchips 

Woodchips are an excellent source of organic matter, but they should only be used in walkways. Wood chips are best suited to systems with fairly wide bed spacing to avoid ending up with woodchips under your beds. Woodchips have a very high carbon to nitrogen ratio, and so they will pull nitrogen away from your crops if placed too close to the rooting zone. Over time, woodchips can add a substantial amount of organic matter and are excellent for absorbing and retaining moisture. Many growers are able to obtain woodchips for free by working with local arborists. Check with your certifier before using woodchips if you are an organic grower, as you may not be able to trace the source. 

5. Wool mulch (woolch) 

Wool mulch was researched extensively in the early 2000's. It is based on the byproduct wool from various industries in Minnesota, and showed great promise. Unfortunately, the product was never fully commercialized. You can read more about it here. While this is not a commercially available product at this time, I am mentioning it to spark ideas among growers who may have sheep farmer friends and neighbors. 

There are many other materials that can be used as mulch in small-scale systems - leaf litter, bark, etc. but these materials tend to be less abundantly available for larger-scale farms.  

Living mulches

1. Between rows

White clover has been the go-to between-row cover crop for many growers. It establishes well, can provide habitat for beneficial insects, and fixes nitrogen. There are a few drawbacks to using it, primarily that it tends to spread quickly, and so keeping it out of beds can be a challenge. White clover responds well to mowing and should be mowed prior to flowering in order to keep a well-established stand. Make sure that your rows are wide enough to accommodate a mower if you go this route. 

I am a big fan of crimson clover. It (usually) dies over the winter in Minnesota, and is less aggressive than white clover since it has a taproot rather than rhizomes. This also makes it easier to kill. It tends to be slow to establish, and does best with a "nurse crop" like oats. The oats get established first and help keep weeds down while the crimson clover slowly grows, and eventually outcompetes the oats after a mowing, or when the summer heat kicks in.

The UMN Student farm has been using white clover
between rows for years. Photo from their blog. 

2. Within rows

One of the primary challenges to incorporating cover crops in vegetables is the short window of time between harvesting late summer and fall crops, and the first freeze. One approach to getting a cover crop in early while providing some weed control is to underseed your cover crop directly into your main crop. This practice is more commonly discussed in the context of field crops, but vegetable farmers are beginning to experiment with it more and more. There are a number of caveats to consider with this practice: you need to plant your cover crop late enough for your primary crop to become well established, or the cover crop can out-compete your primary crop. Typically seeding is recommended after your final cultivation pass, or right before the canopy begins to fill in. However, this means that your cover crop could become shaded-out by your primary crop if it forms a dense canopy. Therefore, this approach is likely best suited to upright crops with a fairly slim canopy such as trellised tomatoes or cucumbers, which are less likely to shade out an understory crop than a crop like pumpkins or melons. Keep in mind that a cover crop growing underneath your primary crop will compete for nutrients, so it must be fertilized. This system can also increase the overall canopy humidity, which may impact disease management; if possible, choose a low-growing cover crop. 

While this type of system is attractive for many reasons, it takes trial and error to figure out the best approach for your farm. Projects like this are great candidates for on-farm research grants such as the MDA Sustainable Ag Demonstration Grant or the SARE Farmer Rancher Grant. Our team can provide support and feedback to farmers who want to apply to these programs. 

Plastic mulch recycling services

For growers who are sticking with plastic, there may be recycling opportunities available in your area. Revolution Plastics may be an option. Recycling Association of MN also lists a few sites that accept agricultural plastics.