Tips for soil temperature

[tqn626]

Anyone got any advice for raising the temperature of your soil? Planning to grow some melons. I heard you can put a woody layer of compost at the bottom of a hole, would that actually work?

[Redbaron]

Originally Posted by tqn626

Anyone got any advice for raising the temperature of your soil? Planning to grow some melons. I heard you can put a woody layer of compost at the bottom of a hole, would that actually work?

It is how I heat my low tunnel for starts. How well it works depends on how bioactive your soil is.

In my case I use mostly fresh manure and only a little wood. It heats faster and more reliably, but doesn't last as long. But I only need it to last long enough to grow my potted seedlings.

For long term, it requires a healthy bioactive soil or else the wood will just sit there entombed and decomposing too slow to make a difference.

However, I have heard about an alternative method that I haven't tried personally yet. So take this with a grain of salt. Apparently instead of digging a hole and putting wood in the bottom, you can also build a raised bed using Hügelkultur. It is a sort of blend between Lasagna beds and Hügelkultur.

What you do is lay first the large sticks and small logs, then fill the spaces with compost making a mound. Then you do your normal lasagna bed including paper layers above that making the mound even larger. Level the top and plant your melons. Supposedly this works great, but as I said, I haven't tested it yet.

I have buried the wood in a pit like you first suggested. Sometimes it works, sometimes not. It isn't a bad thing either way because the wood still helps deep subsoil water retention, especially in very sandy soil. But not always any significant heat.

If you try it, I would be very interested in your results.

[Stvrob]

I bet if you were careful, you could bury a coil of insulated nichrome wire. Do some calculations to figure out how much power it would require to do the job and work backward from there

[Marcus1]

I use green plastic mulch on my melon beds and install tunnels with clear perforated row covers over the top. The plastic mulch is opaque and allows sunlight to warm the soil by several degrees. It keeps the weeds down and pretty much stops evaporation. The tunnels protect the young plants from wind and help the warming. Depending on the year I usually keep the tunnels on for the first 3 - 4 weeks. The melons mature about 2 - 3 weeks earlier with the tunnels than rows without. I also use blue mulch on watermelons, red for tomatos, and white on black for the cooler crops.

[tqn626]

Interesting advice, i will check them all out.

[OldHondaNut]

Raised beds get warm much earlier.

Mulch tends to insulate the soil from warming. Mulch later.

I would NOT put woody mulch at the bottom of a hole. Woody mulch needs air. Underground it would take all the Nitrogen out of the soil.

[sio2rocks]

I have a high tunnel over part of my garden (around 8 ft. Tall at peak, 12 ft. wide and 20 ft. long) and under it are my beds I want the warmest. On these I have black plastic mulch (the really cheap thin black kind about $3 for a 3x25 ft. roll). Even without ends on the high tunnel the ground under the black plastic stays about 10 to 15 F (sometimes 20 F) warmer than the outside ground when temps are down in the 40s F during the daytime (higher when they get into the 60s). This is huge advantage for tomatoes and other crops that need warm soil to grow well. I can set out tomatoes 3 weeks early in such an environment. If I know really cold weather is going to come late I will put ends on the high tunnel and cover the plants with some frost blankets for a little extra warmth.

I usually have tomatoes about one month before other people in my area!

Just one method to think about. I have access to cheap greenhouse plastic so the high tunnel is easy for me to put up every year. May not be a quick solution for everyone.

Colin

[tqn626]

Originally Posted by OldHondaNut

I would NOT put woody mulch at the bottom of a hole. Woody mulch needs air. Underground it would take all the Nitrogen out of the soil.

That what I heard too.

[Hotwired]

Originally Posted by Marcus1

I use green plastic mulch on my melon beds. I also use blue mulch on watermelons, red for tomatoes, and white on black for the cooler crops.

I guess I'm missing the point of colored mulch other than the aesthetics. Is it different heat absorptions, light reflections, ?. Can you elaborate?

Originally Posted by sio2rocks

I have a high tunnel over part of my garden and under it are my beds I want the warmest. On these I have black plastic mulch (the really cheap thin black kind about $3 for a 3x25 ft. roll). Even without ends on the high tunnel the ground under the black plastic stays about 10 to 15 F (sometimes 20 F) warmer than the outside ground when temps are down in the 40s F during the daytime (higher when they get into the 60s). This is huge advantage for tomatoes and other crops that need warm soil to grow well. I can set out tomatoes 3 weeks early in such an environment.

I like the black weedcloth a little better than the plastic because it breathes. Depending on the crop. I staple it down onto the tops of my raised bed and cut holes to plant (1). That really keeps the soil temperature up there. Most of my garden is double-dug raised beds, so I have them setup for row covers (2). My outside tomatoes are weed-clothed, and then mulched with straw (3), This holds the soil heat and moisture. The other thing we both do is grow inside of high tunnels (4). Like you, I like having tomatoes before anyone else and 45 days after everyone else is done.

[Marcus1]

[QUOTE=Hotwired;331503]I guess I'm missing the point of colored mulch other than the aesthetics. Is it different heat absorptions, light reflections, ?. Can you elaborate?

I think its Cornell University has a bunch of info on the advantages of the different colors. I know red reflects red wavelenths that help keep the distance between nodes on toms shorter and also helps in soil warming. The white on black I use on the cooler crops like cabbage, broccoli, lettuce, and cauliflower. The white side is installed up and no sunlight can penetrate the plastic and the soil stays much cooler. The reflected white light is supposed to help disorient insects. The green and blue both allow sunlight through to strike the soil and are more effective than black at heating. It is also the reflected light that stimulates the plants. Some of Cornells field tests showed an increase in production and speed to harvest. I use about 12k feet of plastic each year and its less than 10% of the price of the woven fabric. And it does look pretty in the field.

[Marcus1]

Sorry about that, I don't think I did the reply right. Still learning.