Soil testing for acidity and alkalinity

[Millymollymandy]

A couple of us have gone off topic in another thread and started discussing possible problems with doing soil tests using those kits you can buy.

If you look at the end of this thread could anyone who knows about these things please advise?

http://selfsufficientish.com/forum/viewtopic.php?t=1950

You have to scroll down about 6 or 7 posts until you come to where we went way off topic!

[albert onglebod]

We've got one of those soil test guages from Wilkinsons.
Its a guage with 2 rods that you push into the earth and measures moisture and light levels aswell.
I bought it instead of a chemical test because I knew it would be reuseable year after year.
I test each bed and add lime if its too acid or compost if its too alkaline.
Cant understand why they say to take bits from all over and mix together because it must depend what was growing in each place last and what you want to grow there next.

[Stonehead]

I test my soil annually, plus any additional soil moved in. I take a sample from three places in each bed (20 beds!), plus under the apple trees, the soft fruit, the pig pen, the chicken run, and at various places in the field depending on what I'm intending to do.

I use a professional soil testing kit intended for garden centres, market gardeners and professional growers. It's the HI-3896. I also use a pH meter for spot checks. If you have the money (and they're not cheap), then a soils and liquids conductivity meter is very useful for telling you when soil is too dry or lacking in potassium and nitrogen).

The same company has a good why, when and how on soil testing here.

I would have liked to have had the soil tested by a lab, as baseline to compare with the soil testing kit, but couldn't afford this.

Our soil is very acidic, varying between 5.2 and 6. In the permanent pig pen and chicken run it can dip below 5 in places, which is why the animals get rotated, with the soil limed and rested. (Although potatoes should grow extremely well when following the pigs in particular.)

Acidity between 4 and 5 is often associated with high concentrations of soluble aluminium, managanese and iron, which can be toxic to many plants. Bacteria are also hindered by strongly acidic soil, which means organic matter won't be broken as effectively or as well and that can mean nitrogen is not released.

And, of course, phosphorous uptake is best with a pH of around 6.5 while most other nutrients are best taken up between 6 and 7.

But heavy and repeated liming can make the soil alkaline (lime has a pH of 12), so you want to apply just enough lime for the plants you're intending to grow and at the right time.

So, that's why you need to combine a soil testing programme with good crop and animal rotation, with pH being adjusted at the right time. Applying lime, bonemeal, spent mushroom compost and hardwood ash moves pH upwards; applying sulphur, aluminium sulphate, sawdust, composted leaves, leaf mold and manure moves pH downwards.

If your soil is alkaline in an otherwise acidic area, it can be down to a couple of things - over-liming, leaching of lime from uphill sources, and building wastes (from concrete and mortar). So if you have a newly built house or an extension built from bricks/stone and mortar, then you may get alkaline areas near the walls and anywhere the builders made concrete/mortar or dumped their waste.

Hope this helps.

Stonehead

[Hillbilly]

God thats great Stonehead thanks. Had a look at that kit and now saving pennies for one.

So my 'akaline in an otherwise acidic area' anomaly could be down to leaching after all then from the feild behind. We are directly, slap bang down hill from it.

(Its not a new house and no extensions and we don't grow anywhere near the building.)

cheers

[Millymollymandy]

I bought a pH meter years ago only it was a dud. It told me my soil was acid when I was living in limestone mountains!!! I threw the bloody thing away.