If your tomatoes are under the visqueen they will cook if you are not careful.

Just curious why you chose to use clear rather than the normal black?

What I'm wondering is, minus a heat wave of anykind which is highly unlikely in March and early April here, will it be ok to leave it down until then or will it get to hot even though the weather stays mild with the sun beating down on the visqueen?

It can kill the beneficial soil bacteria but otherwise if there are no plants in the bed I'd think it would be ok. You can always put a layer of mulch on top of it to cool it down or you can cut out strips where the plants will go and leave the rest. It all depends on what you are trying to accomplish. In your zone and in raised beds the soil would warm enough all on its own usually.

Dave

Dave- I went with the clear stuff because its what I use in my line of work so its what I had laying around. I guess I should have been more clear about what I'm doing here. I want to raise the temps in my beds earlier than they usually warm their selves. I plan to plant soon and yes I was going to leave the visqueen down for a bit, but I will be cutting an 18" diameter hole where ever I'm making a tomato/pepper planting. I measured the soil temps in these beds this morning with a 6 inch digital insta-read thermometer and got a reading 54 degrees. The funny thing is when I went to measure my seedlings soil temps in their 16 ounce cups they were 6-7 degrees cooler.

So how hot is too hot for the beneficial soil bacteria? If I cover the plastic with some sort of carbon mulch can it stay there all year?

Damon

So how hot is too hot for the beneficial soil bacteria?

You'd have to get well over 120 (compost piles are 140 but they cycle rather than remain steady at that temp) to do any real damage to the soil - happens here in late June to July but don't know when it might peak where you are.

Of course that would be way too hot for any plants. That's why we use 6-8" of straw mulch on top of the plastic mulch - ours is actually pre-perforated landscape fabric. So 54 is no problem and it should let you plant earlier.

Just keep in mind that this won't let in air or water as well as landscape fabric does.

Dave

There are reasons to sterilize soil using clear plastic. Link below to one site talking about some methods, from google, the soil sorum on GW may also address that topic.

Here's an explanation for why, it may also work on tomato fungus diseases?-
"Onions--the most typical disease of onion family members is white rot. This is caused by a fungus (Sclerotium ceptivorum) that can survive in soil for up to seven years. Thus for rotation to offer 100% control the fungus, you may need to not plant onions on the same ground for at least 8 years. That is obviously a very long rotation. Some other control strategies include removing infected plants as soon as they are spotted and taking care not to drop pieces of infected plant into the soil. Soil sterilization may work in infected soils, but it has some disadvantages of it's own. Sterilize a patch of soil by placing plastic sheeting (black works very well and clear is ok) over it and tightly bedding the edges so that they will keep all the heat baking the soil. Leave this on for two weeks during periods of high sun and heat. After, you take the plastic off, much of the the ground any organic matter will have baked out of the soil, as well as the fungus, so you will need to rebuild it with compost, well-aged manure, or leaf litter."

http://en.allexperts.com/q/Agriculture-2377/rotation-onion-agriculture.htm

Here is a link that might be useful: soil sterilization

Dave- ok so that would be why I wouldn't want to leave the plastic down too long, it doesn't let air in. So is this lanscape fabric you speak of really worth it, does it really retain water better than heavy mulching?

hemnancy- i'm not trying to solarize my soil, but thanks for the info.