When we started using biodegradable plastic mulch, we had two people pushing the roll over the soil, while other people behind them shoveled soil onto the edges of the mulch. It was hard work, so we had to be feeling energetic. If we viewed it as a challenge, we rose to the occasion. The next year we invented a simple tool, a stick that goes inside the roll and has rope attached to its ends, so the roll can be pulled by someone standing upright. Much better than bending over pushing a roll down the row! One little issue was that the rope would sometimes get twisted round the ends of the stick. This year's improvement is to have the rope attached to the ends of the stick with swivel clips. This allows us to unclip to take the roll off the stick, rather than struggle to untie the knotted rope! We also threaded a piece of bicycle inner-tube over the rope to make a more comfortable handle.
The person pulling the roll is closely followed by two energetic "Forward Shovelers" with the task of dropping a shovelful of soil about every yard along each edge of the plastic. We don't want to let the Puller get too far ahead, especially if it's breezy! We need to "tack" the mulch safely down on the ground.
Behind the Forward Shovelers are the Rear Shovelers, usually at least four of them. Today, one was taking the photos, and others have disappeared into the shade! So we don't really have any good photos of this part.
It is perfectly possible to store a partial roll of biodegradable plastic mulch from one year to another. Important keys to success are to carefully wrap the roll of mulch to exclude light, and store it on end, fairly vertical. If you lay it flat, the layers of plastic could stick to each other and you wouldn't be able to unroll it. You also need to keep rodents away, and protect the roll from sharp tools. If you need 4,00 feet per year, you could buy a roll every other year. This is generally a better deal than buying shorter pieces.
I buy from Nolt's Produce Supplies in Leola, PA (717) 656-9764. They sell Bio360 BTB645 4' x 5000' for $345 plus shipping, and Eco-One E1B548 4' x 8000' for $243 plus shipping. They don't use email or websites, and they're closed on major Christian holidays, so don't call then! Johnny's Seeds sells 32' lengths for $17.95. Robert Marvel sells whole rolls of Eco-One and Bio360 (Call 717-838-0976 or toll-free 1-800-478-2214 for prices).
We like biodegradable plastic mulch because it warms the soil, and we get much earlier crops. It also keeps the weeds down for a few months, and then it falls apart, so we don't have to remove it and cause heaps of agricultural plastic trash. It's particularly good for vining crops like sweet potatoes and watermelons, because by the time the plastic disintegrates, the vines cover the ground and weeds have little chance of growing.
We qualify our praise is because it has been hard to find out what it's made of, and what it disintegrates into. Biodegradable is not the same as bioplastic, nor as bio-based.
I found a European Factsheet on bioplastics which clears some of the confusion. There are conventional (petroleum-based) plastics and there are bioplastics. Bioplastics are plastics made from biological substances rather than from petroleum products alone. Some are biodegradable, some are not. Bioplastics may be divided into three categories.
Bioplastics which are not biodegradable. Oxo-biodegradable plastics (made partly from natural sources, partly fossil-based materials, with non-biological additives) — they break down into fully biodegradable materials.
Bio-based biodegradable plastics made wholly or in part from vegetable material. This type are often made of cornstarch, but could be made from other agricultural crops.
The two most commonly available biodegradable plastic mulches in the US are Eco-One and Bio360 from Canada. Novamont, an Italian company, imports Biotelo, the original mulch film made from their product Mater-Bi.
Eco-One describes itself as Oxo-degradable. It claims "Environmentally sound degradation: Laboratory studies indicate that this degradable plastic breaks down into CO2, H2O and biomass without toxic residues. Degrades fully both above and below the soil." It's available clear (for encouraging early emergence of sweet corn) and black, including an extended lifespan version for those wanting a 5-6 month window before it degrades, rather than the usual 3-4 months.
Bio360 is made by Dubois. It's entirely biodegradable, and made from Mater-Bi, a non-genetically-modified starch with vegetable oil resin. Mater-Bi® is a wide family of fully biodegradable bioplastics, sold in pellet form to the industry of bioplastic converters. Mater-Bi®'s ingredients consist of plant starches, "mainly corn starch, with fully biodegradable aliphatic-aromatic polymers from both renewable raw materials (mainly vegetable oils) and fossil raw materials. Mater-Bi breaks down into carbon dioxide and water, with no mulch residues in the soil." (see also the Cornell University 2006, Biodegradable Mulch Product Testing).
Ah! So even Mater-Bi contains some fossil raw materials. And of course, fossil fuels are used in the manufacturing process. Life is so full of trade-offs!
I found explanation of the chemistry from the Biodegradable Products Institute, as part of a 2012 petition to the USDA National Organic Standards Board to allow "Biodegradable Mulch Film Made From Bioplastics". Their claim was that the bioplastics they were petitioning for are not polyethylene like regular plastic mulch, but are fully biodegradable and should perhaps be considered as a soil amendment rather than a plastic. The Organic Standards permit “mulching with fully biodegradable materials” but require that “plastic or other synthetic mulches . . . are removed from the field at the end of the growing or harvest season.” In other countries, these biodegradable mulches are acceptable under organic standards.
The first biodegradable plastic we used was Bio-Telo, (Mater-Bi). Since then we have sometimes bought that and sometimes Eco-One. I had not appreciated the difference. Knowing what I know now, I'll buy the Mater-Bi types in future, rather than the oxo-biodegradable ones. We want biodegradable bio-based materials.
To read more about biodegradable mulches, particularly the chemistry and the petition to the USDA Organic Standards Board, (and much else) go to my website SustainableMarketFarming.com/.
Top photo Unrolling the biodegradable mulch and setting it out by hand.Wren Vile
Second photo: Pulling the biomulch roll using the special hand-made tool. Wren Vile
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