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KENTUCKY

As spring approaches, alot of people will be doing various things to warm up the soil. I will be putting plastic down, probably. My question is, is it better to use clear or black plastic for this purpose? Or is there a better way, or other suggestions? I know I will not be going to the expense heating cables.

Thanks,
Mike Schroeder

2/21/2004 9:25:25 AM

Garden State Pumpkins

Hey Mike, I would go with the black plastic...something about the black plastic absorbing the sun rays whereas light colors reflect sun....There probably is a much better explanation or scientific word for it but that is what I've been told....wait for more inteligent responses then this one. Chuck

2/21/2004 10:39:59 AM

This isn't a more intelligent response than Chuck's by any means, but I will mound up the soil inside my hoophouses so it heats fast. I might break down and buy a soil heating cable as well, and I might use a space heater at night (more for the air than for the soil).

2/21/2004 11:25:58 AM

[email protected]

Anyone have a good price on heating cables? Anyone have a good price on a black plastic roll? Just thought this thread could use a few good suggestions to these topics.

2/21/2004 12:57:26 PM

Cornwall UK.(50N 5W)300ft.

Chuuck's right about light colours (white) reflecting they keep the soil cool but clear stuff lets the heat go straight through and traps it like in a greenhouse.Black plastic attracts heat and then the warm plastic in turn warms the soil.Clear gets my vote.

Mark

2/21/2004 2:06:47 PM

Goffstown,nh

Mike, I do my starter pits then mound the soil slightly. Each mound has a 30' heating cable wrapped in a spiral. (purchased these cables at Charlies Greenhouse Supply). The cable is burried a few inches beneath the soil. I then place a 5' x 5' sheet of 6mm black poly over the mound and cables.(soil temps will stay above 60 degrees 24 hrs. a day) I then build my mini hoop house over the entire mound. When vines start to run i cut the poly out, and remove all cables for the season... This has worked well for me.
Jim

2/21/2004 2:44:11 PM

Wisconsin

You would sure think that black plastic would work better but I have tried both (and monitored the soil temps with a temperature probe) and clear plastic will heat up the soil much better. Black plastic will absorb sunlight and get very warm itself but not as much heat gets down to the soil. Clear plastic, on the other hand, allows the heat to get down into the soil and then acts as a greenhouse to hold it in. Try it yourself but I have found that clear poly works better.

I also have 4 soil heating cables sitting up in my attic that I don't even use anymore. With clear poly it is not hard to heat up the soil. The problem in the spring is heating up the cool air at night around the plant. Soil heating cables don't help much with this and from my experience aren't needed much for the soil itself. In fact the ones I have have thermostats and most of the time the soil is warm enough that they aren't even on. I do use lights in my cloches though to heat up the air at night around the plant.

2/21/2004 4:28:30 PM

Long Island,New York

clear poly with an air layer between the plastic and the soil.

2/21/2004 5:04:03 PM

Garden State Pumpkins

Thanks I learned a bunch from this post already!...laying in bricks for the air layer??? 2inch...4 inch???

2/21/2004 6:15:24 PM

Long Island,New York

I just used small branches that fall off the maple tree..they curve somewhat and allow for up to 4inches air.....like a little greenhouse....readily available too...G

2/21/2004 6:45:05 PM

KENTUCKY

many great ideas have come up. Thanks eveyone!!

I know alot of people do the greenhouses and mound areas, another question? If your trying to get a plant going early for an early fair in the summer, would it be a good idea to try to get all the 600sq. ft. area (in the ground) warmed up quicker by using the above methods?
What i'm getting at is by the time the vines have run and got to the outer area's of the patch, the air temp will be good, but won't the ground temp just under the surface still be cool in the outer areas? So i'm guessing that it would help to warm those areas(below the surface) up in the outer areas before the vines get there??

Thanks again,
Mike

2/21/2004 6:56:30 PM

[email protected]

Clear plastic over a small air chamber warms up faster. But it cools off quicker at night too. The bigger the chamber the less quickly the temperatures change. The higher the plastic can be (within reason) the better so long as it can be held secure. If it's too high & the wind gets under it all the insulating effect is gone.

2/21/2004 7:36:53 PM

Ljubljana, Slovenia

In theory black plastic should warm AND cool faster. It behaves lake a black body (e.g. the black hole in space) that is it has high capacity to absorb and emit radiant energy (infrared-heat, visible-light,..). The opposite is a white body, which absorbs and emits minimal radiant energy. It looks white because it reflects light and stays warm longer because it radiates less. That is why eggs are white: they do not cook in the sunlight and stay warm longer.

Transparent plastic produces greenhouse effect because it transmits incoming energy (light), which heats the soil. Most of the infrared radiation, which radiates from the warm soil, is then captured (reflected or absorbed) by the plastic.

I wrote this to stay away from some urgent work.. I usually do not complicate that much. Jernej

2/23/2004 4:28:46 AM

Ljubljana, Slovenia

Another thing: last year my pile cooked (more than 60°C!) because of too much chicken manure. The principle is that microorganisms feed on a mix of organic and mineral nutrients and produce heath as they grow. So with the appropriate soil mix you may not need heath cables.

2/23/2004 5:15:44 AM

[email protected]

Test in progress in my patch.

Black rubber pond liner.

Black woven poly tarp.

Clear 6 mil plastic suspened.

Clear 6 mil plastic on the ground.

All went down last weekend. I'll start soil temperature testing this coming weekend to see which is warming up the best.

Steve

2/23/2004 9:04:33 PM

Norton, MA

OOOOH, great idea.

2/24/2004 6:08:37 AM

Chippewa Falls, WI

Ahhhh come on Steve what about a good old fashion hot pit..Using some fresh manure to add to your list..

2/24/2004 9:12:12 AM

KENTUCKY

thanks Steve, are you going to post your results this weekend?

Thanks,
Mike

2/24/2004 11:46:59 AM

[email protected]

I added perhaps too much manure last fall & it was fresher than I would have preferred. But it's all tilled in now.

I'll post the results.

2/24/2004 11:57:23 AM