I've been following the discuss and was hoping to get some help. We are preparing to install a mainly will cherry orchard, following the amazing ideas of Stefan and the permaculture orchard
but I need some insights regarding the plastic mulch in an orchard were the summer temperatures reach 43º easy? We are conserned about the soil life and roots boiling in this kind of heat, etc...
I've been searching in all the foruns and websites I can get my hands on, and still haven't found an answer regarding this subject.
Would white plastic mulch help? I know that some plastic used in vegetable production is white on one side and black on the other. If the white side is up, it reflects the light and keeps the soil and roots cool. I don't know if it comes in the thickness as recommended by Stefan.
Hugo, you already know the answer to that.
Plastic is not mulch in our climate, black plastic it's an used technick called insolarization? (solarização) Check it out.
Wouldn't hay or leaves be more cheap also?
Hugo, I absolutely agree with Andre. Plastic is poison. It will break down in your soil and leave its chemicals there.
Plants need rotting organic matter. Very thick mulch of leaves, mowed grass, compost, mowed weeds (small particles) layered very thickly, a minimum of 6 inches in a donut shape around the tree, out as far as the branches extend, will help hold moisture in the soil, save on watering. Our main goal is to feed our soil critters, so ask yourself whenever you put something on soil, how will this make the soiler richer and create more soil critters?
Don't fall for the My-Place-Is-Special, It-Won't-Happen-Here Syndrome.
Andre and Cristo are right on the money, listen to their sage advice.
It is always better to use organic materials for mulch, part of the process of mulching is for that mulch to decompose and add nourishment to the soil beneath it.
Plastics are not good for anything that wants to grow, there are very nasty components to all plastics; cyanide, ether, carcinogens are just a few. Do you really want to grow something you will eat in or around stuff like that?
Some of the best soil on the planet is the result of many layers of plant litter decomposing and leaching into the dirt beneath the litter.
Permaculture is the imitation of Mother Nature's methods of soil improvement, adding man made materials is counter productive at best.
As Andre mentioned, Hay, Straw, Leaves, Manures, grass clippings, crop refuse, all are great components for mulching. Wood chips are also good and they last longer. I like them for the top layer of mulches, they also hold everything in place while it rots.
As Cristo mentions, the main purposes of mulch are to 1. retain water from evaporation. 2. enrich the soil beneath the mulch. 3. provide nourishment for the microbiology of the soil and the worms that come to feed on all that goodness you have put on their dinner table.
The only place that plastics or rubber is actually a good thing (to my mind) is on a play ground, where it can last forever and provide some cushioning when children fall from the swings or slides or climbing bars. For plants these materials are poison, the only thing they do that is good for plants is retain moisture. That moisture most likely is being contaminated by the compounds that leach out.
If you really need something other than the above mentioned best bets for mulch, use fabrics like cotton or wool, these are natural fibers which will break down over a year or two.
Back to Hugo's original question (which IS about plastic as Stefan uses in the permaculture orchard video), Stefan was using an exceptionally thick plastic mulch because it had a much longer lifetime than the usually used plasticulture. Stefan also pointed out that organic mulches didn't work for him and my experience is in line with his. If you need to mulch any sizable area (i.e. larger than a small garden), you will spend large amounts of money and time on the organic material mulches. The weeds will almost certainly penetrate the mulch in relatively short order and you will spend your time dealing with that problem. If you have a small orchard like Paul Gautschi (sp?) in the Back to Eden movie, then mulching with wood chips or other organic material will work well. I totally agree with others posts about the benefits of organics and the drawbacks to plastic.
The black plastic will definitely heat up the soil. If you can only find the thicker plastic in black, I'd suggest some sort of whitewashing (maybe a lime mixture?) to reflect the light up to the plants. I have had decent luck using landscape fabric on top of the soil for annual vegetable production. I burn holes in it for the plants and pull it up at the end of each season. I am on my fourth year of reusing the fabric and it has drastically reduced weeds and help plants grow in my relatively cooler climate. The weave of the fabric allows rain water and air to penetrate and the cover helps keep moisture from evaporating from the soil. Any time I have pulled back the fabric, the soil beneath is teaming with life. I do not recommend using the fabric underneath another mulch, but have it on top of the soil. As the plant canopy grows out, it shades the fabric and I think eventually the extra heat isn't an issue.
Justin, how cool is cool up where you live?
Like Hugo said, temperatures in the summer can reach +40ºC and the average between 12-17:00 hours are for sure +30ºC. You also made a remark that i did not think about, wouldn't a big percentage of the rain that falls in the winter not infiltrate in the soil with the plastic? In this country black plastic is usually used as mulch for aromatic plants, the temperatures under it are very high and all plants die under it...
Where i live (south Portugal) a 20 kg hay bale costs 2.5€.
Hugo, buy a 20l black or white vase, fill it with compost, put it outside all day and keep checking the soil temperatures. At 18h you cannot touch the vase ahaha
Also, check the guys at Herdade do Freixo do Meio, Catarina and Carlos, they used hay as mulch in their commercial orchard, ask their opinnion on the subject.