Clear Plastic vs. Black Plastic for ROASTING Grass/Weeds

Weed_Bouquet_3

Does clear plastic or black plastic work better for solarizing the soil?

On Friday I posted on getting rid of St. Augustine grass… and then, serendipitously for all of you, my recommendation of black tarps to kill grass was challenged by an article from NoTillVeggies.org*:

 

“I’ve got some data and I’ve got some pictures. Both are really interesting. If you missed the first post on this project, check it out here. So far, clear tarps appear to be killing cover crops and weeds quickly and effectively- more effectively than black tarps.

clear plastic vs black plastic

Carolyn checks out the difference between clear plastic (bottom) and black plastic (top) after two weeks of the tarp treatments.

Seamus overseeing his crimped and tarped masterpiece.

Seamus overseeing his crimped and tarped masterpiece.

A quick re-cap. Seamus, eager undergraduate researcher and able farm hand in the Agroecology Lab here at the University of New Hampshire, wanted to look at no-till transplanted cabbage into a rye-vetch mulch. He had access to a roller-crimper, but we had a feeling that just rolling-crimping would create two problems: it might be hard to kill both the rye and the vetch at the same time, and we wouldn’t have enough biomass to create a long-lasting weed suppressive mulch. We don’t have biomass data yet, but while this cover crop performed nicely, it didn’t have the super high biomass as is required to create a really thick, weed-suppressive mulch.

To address the anticipated problems of not completely killing the cover crop and having weeds present, we wanted to look at different tarp types and durations of tarp treatment. We therefore ended up with three “tarp” treatments: black tarp (“occultation”), clear tarp* (“solarization”), and no tarp…

 

I highly recommend reading the complete post. Their results thus far are compelling. I love seeing research like this and congratulate and thank them for sharing their data so we can all benefit.

Two thumbs up!

 

*h/t to Mart for sending the post my way.

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4 comments

  • I have slightly opaque 2mil plastic drop cloth tucked into a raised bed like a blanket right now. I put a thick layer of chop and drop garden cleaning and dry grass clippings down, watered it all in then put the plastic on. I stuck a thermometer in and it is 145 degrees at the surface, composting temperatures for the mulch layer, and 94 degrees at 5″ deep. Take that nematodes!

  • Thanks for the great reference, David! I saw that the first post in their series has a feedback form ( http://notillveggies.org/2016/05/26/tarps/ )- I recorded my own experiment there to kill Bermuda grass, hoping more people will chime in.

  • It appears they have an update now that the black plastic ended up working better in the end, at least under the conditions for their experiment with the thick grass.

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