Okay, from the books I read:
Lime (calcium carbonate) will raise the Ph of your soil quickly, ground dolomite (calcium and magnesium carbonates) will also raise it, but not as fast. Builder's lime will do the trick. The amount to use should be roughly 100g per one square metre of top soil for sandy soil, 200g for loams and up to 400g/m2 for clay. It will take a couple of months for the builders limestone to work, and about a year for the ground limestone. This is how we raise the Ph on our farm, we add between 1 to 2 tonnes per hectare, and it should last for 3-20 years, depoending on a number of variables. The Ph drops for us because people have basically been mining the soil, taking grain and grass (includes hay) without returning much to break down in the soil, so becomes acidic over time.
To lower Ph, Sulphur in many forms can work, and so can Iron Sulphate, although it is more expensive.
For a pot, with a Ph of 2, I cant imagine much would be growing. When you hit that stage, aluminium toxicity becomes a real problem. I would probably throw two good handfuls onto the surface of the pot, and give it a light sprinkle. The water is not so much to blend it in, more to stop it getting blown away when the wind comes.
I would have to say do not buy one of those Ph probes you see around the place, I cant remember what sort you said you have already got. They are usually wildly inaccurate, not the thing you want to be measuring with. The liquid testers are great for hydro growers, but if you are a soil grower, you need a soil kit. You can make one of the other ones work, but I think its simpler to just get the right thing in the first place.
Do you know why your soil is so acid?
Lime (calcium carbonate) will raise the Ph of your soil quickly, ground dolomite (calcium and magnesium carbonates) will also raise it, but not as fast. Builder's lime will do the trick. The amount to use should be roughly 100g per one square metre of top soil for sandy soil, 200g for loams and up to 400g/m2 for clay. It will take a couple of months for the builders limestone to work, and about a year for the ground limestone. This is how we raise the Ph on our farm, we add between 1 to 2 tonnes per hectare, and it should last for 3-20 years, depoending on a number of variables. The Ph drops for us because people have basically been mining the soil, taking grain and grass (includes hay) without returning much to break down in the soil, so becomes acidic over time.
To lower Ph, Sulphur in many forms can work, and so can Iron Sulphate, although it is more expensive.
For a pot, with a Ph of 2, I cant imagine much would be growing. When you hit that stage, aluminium toxicity becomes a real problem. I would probably throw two good handfuls onto the surface of the pot, and give it a light sprinkle. The water is not so much to blend it in, more to stop it getting blown away when the wind comes.
I would have to say do not buy one of those Ph probes you see around the place, I cant remember what sort you said you have already got. They are usually wildly inaccurate, not the thing you want to be measuring with. The liquid testers are great for hydro growers, but if you are a soil grower, you need a soil kit. You can make one of the other ones work, but I think its simpler to just get the right thing in the first place.
Do you know why your soil is so acid?
hehehe.