northern climate soil temps

[berryman]

A chart I looked at today listed the following values for soil temperatures best for tomato growth;
Minimum 50 deg F
Optimum range 70-95 F
Optimum 85 F

Well, I went out and measured the soil temperature 10" down today and guess what the temp is? Measley 48 degrees! I am quite sure that the soil temperature in my parts never gets to 85 deg.

So this year I have designed an experiment. I will water my plants with heated water 8-12" deep and measure the temperature in the root zone. I will also grow a few control plants in the conventional way so that I can compare results.
I will post some pics tomorrow of my new system.

[Gardeneer]

Minimum 50 deg F
Optimum range 70-95 F
Optimum 85 F

Minimum soil temperature maybe even lower than 50 for tomatoes. But I don't think 85F is optimum. 85F is too high. I would say 75F is max on optimum range. I have read potatoes stop setting when the soil temperature is over 75F. We know that potato and tomato are close cousins. I could be wrong.
Gardeneer

[sjamesNorway]

I plant shallow to avoid the early problem of cold soil temperatures deeper down. If you measure the temperature at 4", you should see what I mean. It's the same technique as "planting leggy transplants horizontally" in these garden notes:

http://www.ext.colostate.edu/mg/Gardennotes/717.html

Steve

[AKmark]

This may help you understand why proper temps are important for good production.
http://nrcca.cals.cornell.edu/nutrie...CA2_print.html

[Gardeneer]

Originally Posted by sjamesNorway

I plant shallow to avoid the early problem of cold soil temperatures deeper down. If you measure the temperature at 4", you should see what I mean. It's the same technique as "planting leggy transplants horizontally" in these garden notes:

http://www.ext.colostate.edu/mg/Gardennotes/717.html

Steve

That is very useful info, Steve. I usually dig a bigger and deeper holes and fill the bottom and around the plant with warmed up soil and also water with lukewarm water.
Right now under plastic cover ( for about 2 months) the temperatures register about 55F at a depth of about 6". That is about how deep I am going to plant.
And I will keep the black plastic on for another 2 months.

Gardeneer

[berryman]

Gardeneer, I think you are right about 85 deg being too much. I did more research and it's of course amazing how many opinions about this there are. From 60 to 85...so I will aim for 70-75 deg F 12" down.
I am quite sure that this is not a natural soil temp where I am and although plastic and other surface treatments will help, I remain unconvinced that whatever is done on top will have much effect down 12".
I have dug a 2' deep trench 20' long and put four big wheelbarrows of old compost in there. Soon I'll post pics and plans on how I plan to heat the soil down there.
Bob

[Cole_Robbie]

Black plastic over raised ridges of soil will speed up the warming dramatically.

[Gardeneer]

Originally Posted by Cole_Robbie

Black plastic over raised ridges of soil will speed up the warming dramatically.

Sure thing. I got it up to 55F

[clkeiper]

Originally Posted by Cole_Robbie

Black plastic over raised ridges of soil will speed up the warming dramatically.

I was going to mention this. We lay black plastic early (we did it weeks ago) to warm the soil to plant earlier. now I am waiting on it to quit getting down below freezing every night... sigh... this just isn't Spring weather for us. I would like to get the cabbage and broccoli and some lettuce planted out. Some of what we lay is reflective and some is plain black.. mostly to get the zucchinis planted sooner than normal.

[berryman]

Gardeneer, your beds look great.
how deep did you measure the soil temp?

Thanks, Bob

[bower]

Black mulch and raised beds or containers are a must for us too.
Another thing I've thought about but not tried, is some kind of modified hotbed.
Layer of hot manure is spread about a foot down, covered with soil into which you put your plants.
The heat from the manure should rise and warm the roots above...

https://thecontraryfarmer.wordpress....r-your-garden/

[Gardeneer]

Originally Posted by berryman

Gardeneer, your beds look great.
how deep did you measure the soil temp?

Thanks, Bob

Thanks Bob

I measured it at about 7" deep . The last time it registered 55F. Now with the recent sunny warm days probably the heat has penetrated deeper.

Before planting I dig a hole about 8" deep any let the soil that came out of the hole spread under sun and get even warmer. Then I put some of that warm soil in the hole, put the plant in and fill back the rest of it. In the mean time my watering can was sitting in the sun getting lukewarm. And I water the plants lightly with that.

Gardeneer

[sjamesNorway]

Originally Posted by Gardeneer

That is very useful info, Steve. I usually dig a bigger and deeper holes and fill the bottom and around the plant with warmed up soil and also water with lukewarm water.
Right now under plastic cover ( for about 2 months) the temperatures register about 55F at a depth of about 6". That is about how deep I am going to plant.
And I will keep the black plastic on for another 2 months.

Gardeneer

I'm going to try some bubble plastic this year, instead of black plastic. I read somewhere that it lets the sunlight in better, and at the same time insulates to keep the heat in. I'll try both, and compare.

[Gardeneer]

Originally Posted by sjamesNorway

I'm going to try some bubble plastic this year, instead of black plastic. I read somewhere that it lets the sunlight in better, and at the same time insulates to keep the heat in. I'll try both, and compare.

I think it might work fine. Clear plastic lets most the sun rays in and reflects some, hitting the soil. Black plasic absorbs the sun an works like a warm blanket.
Clear plast can lose heat via radiation at nigh, but black does not radiate.

Actually I covered my beds with both black and clear plastic. Top layer was clear, to create greenhouse effect.

[berryman]

Here's my new idea for warming the soil.
I dug a trench 30" deep and filled it with native soil mixed with lots of compost. Then I pounded some fence posts in along the north facing side and buried some polyiso sheets 12" deep in the trench.
Just like you can use a south facing wall to reflect the sun and make things warmer, I figured the insulation would do the same. I am going to cover the whole shebang with greenhouse plastic.
The pvc pipes have little holes drilled in them at 12", 16" and 24" deep and I will put heated irrigation water down in the pipe to warm the soil in the root zone.