Today we're going to be measuring a really important soil characteristic, and that is soil pH. pH is a scale used to assess whether something is very alkali on one hand or very acidic on the other hand. The pH scale starts at zero, which is something on the very extreme acidic end of the scale, up to something which is a scale of 14, which is at the extreme alkaline end of the scale. A pH in the middle of 7 is something that we call pH neutral. pH does affect many plants and animals that live within the soil, and in the UK most of these organisms will prefer a pH somewhere in the range of 5.5 up to a pH of neutral which is 7. There are a variety of factors that will affect the pH of your soil, including things like temperature, weather and climate, as well as things like the bedrock geology underneath the soil and the relief of the surrounding area. For example, in very wet areas, some of the cations that would otherwise be stabilising pH get washed away, leading to more acidic soil formation in that area.
So, today we're going to be selecting soil from the site in front of me here. Before we do it, there's a couple of quick pointers.
One - please make sure that you get the permission of anybody owning the land for you to dig those holes, and two - there's tonnes of bacteria growing within that soil, most of which are healthy and will cause you no harm, but some of them do have the potential to do so, so as a precaution please wear gloves if you can, if you have access to them, and before you eat or drink please wash your hands.
Today I'm going to use the OPAL pH test strip that you get in the Soil and Earthworm Survey and also the Water Survey. They look a little bit like this, and I'll be using that in just a second. Before I measure my soil pH, I'm going to need to take a soil sample. I'm taking this from about 10cm depth in my soil pit here, and I'm putting it into a plastic beaker, a plastic cup would also do nicely. I have 1cm depth of soil here, and now I need to add some water to it. The water I'm using today is distilled or de-ionised, and if you have access to that then please use it as it might give you more accurate results. If you don't, tap water is fine too. Fill up the beaker so that the water is covering the soil completely, and the next step is to give it a really good stir for approximately one minute to mix up your soil solution. Luckily I have one I prepared earlier which I'll hold up for you now; so that's been readily stirred already. Once I've got my soil sample, I'm going to be actually testing the soil pH using this colour coded test strip. The more dark blue and purple values indicate an alkaline soil, the more green and yellow values indicate a more acidic soil. I'm going to going to be dipping the middle part of this test strip into the soil sample so it’s completely submerged; I'm going to be waiting for 3 seconds before I then pull it out.
If there's lots of soil on your test strip, you should give it a wash just so that you can see: in this case it's just fine. You should also wait for about 2 minutes, because the colour change can take a little while, before you read the value. Luckily for me again, I've also got a pre-prepared test strip here. If you can make out my colour here is a slightly light green, which in this case indicates a pH value of about 6, which is in that optimum range which means that plants and animals should be able to survive here just nicely.
Soil pH is really important information for many different people, including farmers and gardeners for obvious reasons; they're going to be wanting to grow lots of plants; but also for scientists interested in the biodiversity value of this area, of things living on top of or underneath the soil.