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Clear vs. black plastic to increase decomposition rate?
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Posted by
steve22802 7a VA (
My Page) on
Fri, Feb 25, 11 at 19:26
| I'm making two new garden beds (4 x 25 feet each) this spring over top of existing lawn. I first laid down cardboard over the grass and now I'm piling on manure, leaves and various other organic materials. I'd like to have the turf killed and the amendments decomposed by mid May so that I can transplant into these beds after last frost. I'm thinking that it would be good to cover them with either clear or black plastic to trap the moisture, increase heat, block weed growth and to speed decomposition. Does anyone have opinions on whether clear or black plastic would be a better choice? I know that clear would generate more heat but it might also cause weeds to grow under the plastic. I doubt that it will be hot enough at this time of year for true soil solarization to take place so I'm afraid the weeds would thrive rather than be terminated. |
Follow-Up Postings:
RE: Clear vs. black plastic to increase decomposition rate?
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| Since you have two beds and two options, it`s obvious that you should try an experiment and then let us all know plastic choice was the best. |
RE: Clear vs. black plastic to increase decomposition rate?
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If you sealed the edges of the plastic well enough to do that you would cause the material under the plastic to go into anaerobic (absence of air) digestion, not a good thing because that tends to encourage disease pathogens to grow. Since the bacteria that will be digesting that material need air to live why put an impervious cover over them and deprive them of what they need to do what you want them to do?
If Pat Lansa, in her articles about Lasagna Gardening idicates good results planting in undigested organic matter you should get similar results. |
RE: Clear vs. black plastic to increase decomposition rate?
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| My main source of manure is llama pellets. The problem I have with them is that if they are exposed to air they dry out quickly and then don't decompose properly. I think I can avoid the anaerobic problem by removing the plastic occasionally and raking or tilling the bed. I think maybe clear plastic is the way to go for the extra warmth in the spring. If weeds germinate I can till them under every week or two and then perhaps I'll end up with a stale seed bed by planting time. :) |
RE: Clear vs. black plastic to increase decomposition rate?
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The black plastic laid over the lawn sans all the other stuff should do a half decent job of killing the grass which then could be tilled into the soil.
The time you are attempting to do all this by lasagna method is too short, the plastic ontop of the amendments will surely not make a dent in the killing of the grass under it all.
If you have any spare window panes....I know that's reaching...but if you do or could lay your hands on a pane of glass of size, that could be laid ontop of your turf and makes a very good effective lawn killing. Any grass that has not been killed should be removed instead of tilled lest the seeds come back up to haunt you. |
RE: Clear vs. black plastic to increase decomposition rate?
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| I stopped using plastic sheets in the garden many years ago after realizing it is made from non renewable resources and it kept both air and water from getting to the soil. I have used newspaper and cardboard to create new garden beds instead of the plastic and those have the advantage of providing some carbon to the soil bacteria. The newspaper, or cardboard, hhas killed the grass enough in about 6 weeks to allow planting without the need to till the soil, so a Lasagna Bed made over the area will do the same thing. Since the grass will also provide a nutrient source for the soil bacteria there is no good reason to remove any of it. |
RE: Clear vs. black plastic to increase decomposition rate?
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| Kimmsr, I agree that we should all try to minimize our use of nonrenewable resources in the garden. Perhaps a better approach for me would be to make sure that the llama pellets are well moistened and then to cover them completely with something like grass clippings to retain the moisture. I too have had good success using cardboard to kill off lawn for new garden beds. I used to strip all the sod off but I finally learned that that was way too much work and that the organic material from the decomposing turf will add to the soil quality of the new bed. I do have a number of pieces of scrap glass around so I may try using those instead of clear plastic to increase soil temperature and retain moisture. You know, I think what would really help me most is to have an easy method for crushing llama pellets into a powder. Any suggestions for that? |
RE: Clear vs. black plastic to increase decomposition rate?
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| No suggestions that do not involve a large oven to dry the manure first. The manures I have used over the years have all been composted first before being applied to the garden so the bacteria that digests the compost have already made them into small particles. Where I have helped people do the Lasagna Gardening thing the manures they have added in a few months were not easily distinguished from other material and covering the manure with other organic matter (shredded leaves, grass clippings, etc.) helped keep that manure moist and also reduced any odor from that manure. If too thick a layer of grass was laid in that did produce an unpleasant odor. |
RE: Clear vs. black plastic to increase decomposition rate?
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- Posted by lcpw z6 St Louis (My Page) on
Tue, Mar 8, 11 at 15:52
| Decomposition uses up oxygen faster than most people imagine. I don't have citations handy (sorry!) but I recall reading about experiments done to assess just how fast, and the oxygen trapped within the pile (if no new air was sucked in / blew through) was used up in minutes to hours, not days. I understand wanting to keep things moist. What about using burlap or something like that? They sell a loose weave burlap product that is designed to keep hillsides in place while sprouting grass.... That could help you keep it all moist while letting air in. (Though you may not want to buy anything ... so cardboard might be better if you can keep it in place, or old bedsheets perhaps....) |
RE: Clear vs. black plastic to increase decomposition rate?
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| I would go the way Kimmsr suggests and here's why: I've tried black plastic, clear plastic, and cardboard/grass/compost mixture to try to stop annoying weeds, in three different parts of my yard. I like to experiment. Some places where black plastic has been for almost two years, still has what looks like live weeds sprouting underneath, the clear plastic, of course, didn't even need to be moved to see all the nice new growth of weeds underneath, and the cardboard lasagna style, no sign of weeds for over six months! If the weeds come back after six months, the work and aggravation the lasagna method has prevented, was well worth it. =:) Go lasagna ! |
RE: Clear vs. black plastic to increase decomposition rate?
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| I was out working in the garden today and I stuck a spade in an older bed to see what the soil was looking like. I had turned llama pellets under the soil in that bed last fall now there are big fat earthworms everywhere! :) Now I wish I had made the two new beds last fall and let them sit all winter... ah well, I guess I had other projects going back then. :( Right now I have neither black nor clear pastic covering the new beds because we're getting a lot of rain and I want the llama pellets to stay moist. The more I think about it the more I think I need to build a pellet smasher. I bet the worms would really gobble up the smashed llama manure. :) |
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