Last week I wrote about the chemistry of various biodegradable plastic mulches, and how much we like using them. I promised to write about how we go about setting the mulch out without using tractors or mulching machines. We use maybe 8,000-9,000 feet each year, so we buy whole rolls, one at a time.
The first year we used the biodegradable plastic mulch, we had two people pushing the roll over the ground, as others shoveled soil onto the edges behind them. It was a bit of an Olympic sport, so we had to be in the right mood. If we saw it as a challenge, we did well. Then one of the crew invented a simple tool, a stick that goes inside the roll and has rope attached, so the roll can be pulled by one person, standing upright. Much better than bending to push a roll on the ground! A snag was that the rope would sometimes get twisted up with the stick. This year’s refinement of the tool 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 use our teeth to untie the knotted rope! We’ve also added a length of bicycle inner tube over the rope as a more comfortable handle.
Following closely behind the person pulling the roll we have two energetic “Forward Shovelers” whose job is to get a shovelful of soil on each edge of the plastic about every yard. We don’t want the Puller to get too far ahead, especially if it’s breezy! We want to “tack” the mulch safely down on the ground. Here we are mulching for sweet potatoes, so we have ridged the soil and run out drip-tape.
Behind the Forward Shovelers are the Rear Shovelers, usually at least four of them. This day, one was taking the photos, and others have mysteriously disappeared into the shade, so we don’t really have a good photo of this part.
It is possible to successfully store a roll of biodegradable mulch from one year to the next. The keys to success are to carefully wrap the plastic to exclude light, and store the roll on end, fairly vertical. If laid flat, the layers of plastic could stick to each other and not be rollable. Of course, you also need to keep mice away, and protect the roll from sharp implements. So if you need 4,00 feet per year, you could buy a roll every other year. This is generally a better deal than buying short lengths. As I said last week, 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 for prices).
So this week, our mornings have been spent laying drip tape and rolling mulch, and our late afternoons transplanting. We have done really well this week, and we’ve transplanted all our watermelons and sweet potatoes. This brings to an end our intensive spring transplanting. Now we just have the leeks, the weekly planting of 120 lettuces, and a check on all the existing transplants about a week after planting, to replace casualties. We’ve also got all our T-posts in for our Roma paste tomatoes and started our string-weaving.
We’re having a very busy time in the garden. Because of late cold weather followed by too much rain at once, all our transplanting has been delayed. We’re up-to-date in the permanent raised beds – we’ve planted out lots of lettuce, senposai, early cabbage, scallions, our first cucumbers and summer squash, and chard, tomatoes, eggplant, celery and okra. We’re also up-to-date on raised bed sowings of carrots, turnips, beets, snap peas, snow peas, bush beans, edamame and asparagus beans. But in the row-crop areas, it’s a different story. We have planted out our main-crop cabbage and broccoli, our “spring” potatoes and sown our first corn. We’re about a week behind on our big transplantings of Roma paste tomatoes, peppers, melons, sweet potatoes, and therefore watermelons. It’s also time to sow more beans, cucumbers and squash. But we’re getting to it as fast as we can!
We’ve added in late afternoon transplanting shifts, and some random evening weeding (which has helped us get the first round of carrot and beet thinning done). Yesterday I measured and flagged the areas for Roma tomatoes, peppers, melons, beans, edamame, watermelon, and sweet potatoes. I set out the mainline tubing for the drip irrigation and dropped the shuttles of drip-tape at the ends of the patch. I wrote about our drip tape shuttles a while back. They are part of our commitment to minimize our agricultural plastic usage by making our plastic stuff last. The shuttles let us fairly easily reuse the drip tape.
After running out the drip tape, flushing the lines, capping them off and testing (and fixing!) any leaks, next we’ll roll out biodegradable plastic mulch. This wonderful product has changed our lives! And yet we are not all firmly convinced it is an ecological choice. The language in the accessible information can be confusing.
We like using biodegradable plastic because it warms the soil, leading to much earlier crops, it keeps the weeds down for a few months, and then it falls apart, so we don’t have to remove it and add to the heaps of agricultural plastic trash. It’s especially good for vining crops like watermelons and sweet potatoes, because by the time the mulch disintegrates, the vines cover the ground and weeds have little chance. Why we qualify our praise is because it has been hard to find out what it’s made of, and what it disintegrates into. And for some, there’s that knee-jerk reaction to anything plastic!
Biodegradable is not the same as bioplastic, nor as bio-based. Bioplastics are a type of plastic made from biological substances rather than from petroleum products alone. Some are biodegradable, some are not. Wikipedia distinguishes two types of bioplastics 1. Oxo-biodegradable plastics (made partly from natural sources, with non-biological additives) – they break down into biodegradable materials; and 2. Plastics made wholly or in part from vegetable material. The second type are often made of cornstarch or sugarcane, but could be made from other agricultural crops. Some biodegrade, others don’t (eg those made from sugarcane ethanol). I found the Wikipedia explanations confusing and some read as if they were funded by petrodollars: “It is difficult to see why . . . resources . . . should be used to produce them when the raw material for conventional plastics is so inexpensive and is available in unlimited quantities.” Really.
I found a European Factsheet on bioplastics which clears some of the confusion. There are conventional (petroleum-based) plastics and there are bioplastics. Bioplastics may be divided into three categories. The first is the bioplastics which are not biodegradable. The other two are biodegradable, and differ in whether or not they contain fossil-based materials or only bio-based materials. Our goal would be to get biodegradable bio-based materials.
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”. The bioplastics they were petitioning for are not polyethylene like regular plastic mulch, but “polyesters, polymers formed by the reaction of a hydroxyl group and a carboxyl group. The natural world is full of ester linkages. Living cells and organisms have developed enzymes to hydrolyze the ester linkage. Examples of natural esters are fats and oils, where three fatty acid molecules are esterified to glycerol/glycerin; natural waxes, where long-chain alcohols are esterified to a fatty acid; and some natural flavors, such as banana flavor, n-amyl acetate, an ester of n-amyl alcohol and acetic acid.” Biodegradable bioplastic mulch film materials can contain carbon black to make the film black to absorb heat from the sun. Or titanium dioxide to create white mulch, which can cool surface soil temperatures slightly, by reflecting most of the sun’s heat.
NatureWorks‟ PLA INGEO, Ecoflex® F Blend C1200, Ecovio® F Film and Ecovio® F Blend, Mirel™, were also listed in the petition as suitable Biodegradable Mulch Films made from bioplastics. In contrast, oxo-biodegradable materials were not included in their petition, because they did not fulfill the two criteria proposed to address the concept of “fully biodegradable plastics”.
The Organic Standards are inconsistent, as §205.206(c)(1) permits “mulching with fully biodegradable materials” but §205.206(c)(6) requires that “plastic or other synthetic mulches . . . are removed from the field at the end of the growing or harvest season.”
I’ve been buying 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 are a company that doesn’t use email or websites, and they’re closed on major Christian holidays, so don’t call then! Johnny’s sells 32′ lengths for $17.95. Robert Marvel sells whole rolls of Eco-One and Bio360 (call for prices).
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.
Next time I’ll write about how we set out biodegradable mulches without he use of any machines. Sorry for the delay in posting. I’m working on making improvements to my website, honest!