Biodegradable Mulch Demonstration Update

Tianna DuPont, Scott Guiser, John Esslinger, Andrew Frankenfield, Mike Orzolek, Penn State Extension

We all know the benefits of plastic mulch. Not only does it keep the weeds down, it warms up the soil giving us earlier (and more) tomatoes, peppers, eggplants and other heat loving veggies. But it costs us. Farmers estimate it costs $25-100 an acre for labor and disposal of plastic mulch. A possible alternative to black plastic mulch is biodegradable film mulches that look and act much like black plastic, but instead of ripping them up in the fall, you till them into the soil and the microbes degrade the material, leaving you a clean field (hopefully) in the spring.

What is biodegradable mulch?  Good biodegradables are made from plant starches such as corn and wheat. Soil microbes break down the starch into CO2 and water. Warm, moist conditions that favor the microbes speed up biodegradation. Sticky starches help them adhere to soil, keeping them from blowing away/ littering. The technology has changed from the old degradable films made from polyethylene which degrades slowly and sometimes become dry and brittle, blowing into the neighbor’s yards and hanging from the trees.

How do biodegradable mulches perform? At five of seven sites growers felt Eco-One and Biotelo performed well, sufficiently suppressing weeds and warming the soil. Biotelo seemed to be a bit more fragile than Eco-One. This may be by design to ensure sufficient decomposition over the winter. Two farmers tried paper mulch from Sunshine Paper Co. They were not able to lay it due to difficulties with ripping. In the two sites where the mulches did not sufficiently suppress weeds there were problems with perennials: sedge, thistle and johnsongrass. Sedge and thistles in particular poke right through the biodegradable films. There was no plastic at the site with sedge but sedge is known to pierce even regular plastic mulch. Research by Dr. Orzoleck (2008) found that “Biodegradable performed as good or better than plastic for yields in pepper, cantaloupe.”

Tips to working with biodegradable mulches – The biodegradable films are more fragile than black plastic mulch. Growers found it is critical to release the tension on the plastic layer to keep it from ripping. Just like black plastic, laying biodegradable mulch correctly is important. You want nice full beds with the edges well covered. When the beds are too clumpy or uneven the film will not lay nicely against it and stick to the soil. Loose film then can be battered by the wind and quickly fray. Loose edges will allow the wind to get underneath. There is nothing worse than seeing the wind pick up an entire bed of mulch newly transplanted to tomatoes. Unlike black plastic that you might be able to cover back up later, the biodegradable film becomes sticky when wet and adheres to itself where folded if you don’t catch it right away. Growers also found that if they did not plant into Biotelo or Eco-One right away the mulch became fragile and tended to tear when they were transplanting. This seemed to impact the overall effectiveness of the mulch.

It is important to follow the manufacturer’s guidelines:
• Avoid excess tension when laying.
• Plant immediately after laying.
• Do not store for a second season’s use.
• Avoid transplanting mid-day in higher temperatures.
Additional tips from farmers include:
• Adjust the ‘covering wheels’ on the bed-maker so they do not nick the mulch. Nicks can turn into long tears.
• Use with crops that put on a lot of foliage and shade the soil early.

“When it got hot, it got loose and actually wrinkled. Try to avoid planting in the heat of the day. Keep the tension at the lowest setting to avoid tearing it. Cover the edges well. Don’t walk on it and keep it tight to the ground.” - Andrew, Frankenfield Farm Market

“Just like plastic good bed preparation is important. If the soil is cloddy, and the film too loose it will blow around and is more likely to pull up. If it does it tears easily and sticks to itself. Make sure you cover the edges well. Unlike regular plastic mulch you can’t lay it super tight. I have seen it rip right down the middle from being too tight.” - Tianna, Shooting Star Farms

 “It flops around a little. Be careful with small seedlings.” Harold, Meadow Gate Vista Farm.
 

“It seems that both Biotelo and Eco-One perform better when used with crops that put on foliage or shade fast like summer squash or tomatoes.” Mike, Little Peace. 

 
Aren’t biodegradable mulches more expensive? The cost of biodegradable mulch has come down recently. With 2012 prices Eco-One is $392/A for biodegradable mulch compared to $314-424 for black plastic plus removal and disposal costs. This assumes $80-100 for the labor to remove plastic mulch and $10-100 for disposal.

For more information including pricing and distributors visit see the biodegradable mulch factsheet.

Please see the following descriptions from each demonstration site for more details and advice from collaborating farmers: update and farm profiles.

This project was funded in part with Northeast SARE Pennsylvania State Program funding.