Soil Temp observation Jan 2010

[Dave Brown]

I think it is amazing that when I am actually recording temps and trying to find an explanation for the results, it is just dismissed as warm rain in winter, or a vulcano.

Moved to the Weather and Cimatology section where it may be taken more seriously.

[Conifers]

My (serious) guess is you're right with the reasons, but it would be worth searching for any other potential heat sources - do you have any info on the history of the site, could it be on top of an old landfill perhaps? Or any upwelling of ground water?

[Dave Brown]

Sorry if I overreacted a bit in my previous post, but I believe soil temperature plays a key part in what we can grow.

The site is on part of Chalk Roman Villa, which was part of a string of villas across north Kent, the most Famous being Lullingstone. In recent history it was sheep pasture until the property was built in 1964.

The soil is heavy clay you can make models and pots with. The Washie probe is 2 feet from a wall which is double brick with a foundation of 2 feet in depth. Areas I have dug in the past have a 'marl', I think it is called, subsoil which is a mixture of clay and chalk with huge flints. There is no ground water as we are over chalk.

The location is hot in summer with protection from virtually all directions, however as a result, and being the lowest point in the back garden, with no drain away, may be a bit of a 'hollow' in winter. The temp on my other thermomenter (Butia) fell to 3.5C after the freeze, where as this one (Washie) fell to 1.5C. Both rose to 5.0C a week after the freeze ended.

Washie probe soil gets no winter sun. Butia probe gets morning winter sun.

Currently Washie probe is 6.5C and Butia is 6.0C.

I really could do with a weatherstation upgrade to a Davis Pro, and build a multi sensor proble with readings from 10cm 30cm and 100cm depth..... One day

[stephenprudence]

I imagine my soil temperature at a similar depth is nearer 0C Dave, probably just above. Maybe I'm wrong but I think the soil temperature is quite cool around here, I'd need a soil temp sensor probe though

[Dave Brown]

I imagine my soil temperature at a similar depth is nearer 0C Dave, probably just above. Maybe I'm wrong but I think the soil temperature is quite cool around here, I'd need a soil temp sensor probe though

I very much doubt your temps are that low at 30cm. The probes I got were 16" but if you mark on the spike 10cm, 30cm etc. you insert to the mark leave a few seconds and read off. Mine are permenantly in position. The probes I got are from http://www.weather-station-products.co. ... -2008.html

[stephenprudence]

Thanks Dave, they're quite cheap like a good old traditional soil thermometer!

[Dave Brown]

Not very accurate to read but with melting ice were very close to 0C so less than 0.5C error. Although I would love to get the set up I spoke of to have a continuous temperature read out. I could then compare it with air temps.

[Conifers]

I imagine my soil temperature at a similar depth is nearer 0C Dave, probably just above. Maybe I'm wrong but I think the soil temperature is quite cool around here, I'd need a soil temp sensor probe though

I very much doubt your temps are that low at 30cm. The probes I got were 16" but if you mark on the spike 10cm, 30cm etc. you insert to the mark leave a few seconds and read off. Mine are permenantly in position. The probes I got are from http://www.weather-station-products.co. ... -2008.html

Me too. I helped plant some trees in a frost hollow near the end of the coldest spell in the 1981/82 winter (2 weeks with temps down to -16°C), and the soil was only frozen down to 15cm deep (measured); below that, no ice. A pickaxe got through the frozen stuff fairly easily. Oh, all the trees survived, too, and are still doing well, despite the traditional advice never to plant trees into frozen ground. To freeze 30cm deep I guess would need something like a month of -10°C or colder, sort of conditions you get in northern Sweden or Finland.