I'm looking into using the tarping method popularized most recently by Jean-Martin Fortier in The Market Gardener to help with weed pressure in our permanent raised beds, and was hoping to get some practical advice on materials, timing, and effectiveness from someone that's actually tried it. I have a few questions/ideas:
Does the material need to be water & air permeable? I would suspect that since the method is meant to encourage weeds to germinate and then die off from lack of light (not lack of water or CO2) it doesn't matter if the chosen tarp material is permeable. And I suppose that if the area was effectively air and water-tight (non-permeable material) you would technically be solarizing the beds and compromising the soil biology/earthworms.
JMF recommends using silage tarps, justifying the cost by touting their durability. In looking for cheaper alternatives, someone recommended using rubber roofing membrane (apparently this usually goes into the landfill when buildings are renovated/demolished) cut to manageable size. My immediate red flag had to do with toxins leaching out of the membrane, but I can't find any research to back that up, and in fact it's used in roofing expressly because it does not contaminate the water runoff. Other alternative materials I've seen include polypropylene woven ground cover (aka landscape fabric), and... well... really just that one. Farmtek's fabric remnant section is about the cheapest place I've seen it, but it's a gamble as to what color and weight you get.
Any recommendations as to size or tarp? JMF makes his to fit one full bed, which seems to make sense on a small-scale operation. The rolled-up tarps would be more manageable, but you'd spend more time laying out individual tarps.
Any thoughts or advice out there?
We have been using 20x60' used billboards which are a bit heavy to move, but are OK with two people once unfolded. They can be dragged from one section to another fairly easily and are heavy enough they don't blow around if a bit of weight is placed at edges. They cost about $100 plus shipping. I think we got ours at https://billboardtarps.com/. Depending on weather it seemed like we got a good kill in about two weeks.
Clever re-use! I'm assuming you have to use the black ones? And what is your order of operations from end of one crop to planting of the next, if you don't mind me asking?
By an odd coincidence this video was put up on youtube today, with more details of JMF's tarping methodology. He clearly states that the material has to be waterproof, and landscape fabric/ground cloth won't do the trick.
The Market Gardener with Jean-Martin Fortier Six Figure Farming Part 6 Soil Management www.youtube.com/watch?v=tnqBf6sf2x8
We used the tarps to kill covercrops in the spring prior to the first plantings. It enabled reduced tillage and weed pressure - especially for the first month. We used both black and white ones, and they both worked, but I suspect that the black ones are a bit faster.
Thanks for the billboard tip, I managed to find a smaller company in town (the big guys all have recycling contracts for theirs) and got a small stack. Was really tempted to leave Dolly Parton's 12ft head face-up: