21 May 2010

Experiment of the year: Biodegradable black plastic mulch

I've long known that in climates like mine (chilly Michigan) commercial production of heat loving plants like tomatoes and peppers relies on covering the soil with sheets of black plastic. The black absorbs sunlight to warm to soil, also controlling weeds and keeping the soil moist. But I never realized just how much of an impact it has until last summer, while visiting a friend's research plot, I saw two pepper plants growing side by side, one with plastic mulch, one without. I didn't have my camera with me, so you'll have to use your imagination: The one without plastic looked like the ones in my garden -- small, straggly with a few peppers. With the plastic, the plant was nearly twice as big, lush, full, and covered with fruit. It looked like an ad for some questionable fertilizer.

That impressed me, but I still wasn't willing to try it in my garden, because of the waste. The plastic can only be used for one or two years, then you rip it up and throw it away. Vegetable production in Michigan produces tons of this trash every year, and the idea of adding to it didn't appeal to me. (I have to throw in here a random strange fact: Organic vegetable growers are allowed to use plastic mulch, but under the condition that the replace it every single year rather than leaving it for two years are conventional growers sometimes do. Does that make ANY sense? How is it more "organic" to produce twice as much plastic trash as you need to?)

But I finally decided to give black plastic a try when I saw biodegradable soil warming mulch for sale in the Johnny's Selected Seeds catalog. They say you can just put soil on it at the end of the year, and it will be gone by spring. The flip side, I guess, would be that it might break down too quickly. We'll find out.

So far I can only say one thing for certain: It sure is aint pretty. Here are my new raised bed before:

And here they are after putting the plastic down and sticking some of my seedlings:

Yuck. After last year's dismal tomato and pepper season, I'm willing to do just about anything to ensure I have a good crop this year, but that is REALLY ugly. Those peppers better take off quick and cover it up.

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