This by pop22 sums it up perfectly and could be a must read one line chapter in a grow guide for beginners:
PH rises and falls constantly, and is influenced by many factors. However, unless something is wrong to begin with, I doubt the changes will push the ph into a state thats too low or high.
Start with good medium and good water and off you go. But just if the wheels start coming off and you can't resist putzing around with it I agree with Trapper. The Accurate 8 is the way to go. Runoff water is a chaotic brew gathered at a chaotic moment. FWIW customer support people at Fox Farm, General Hydroponics, and Sunshine Advanced say runoff water is NOT a good gauge of what's going on at the roots. I got this from Fox Farm:
[FONT=&]Accurately testing soil pH requires expensive lab equipment that is not available to most home gardeners. Soil pH testers purchased at your local garden center can give variable readings based on soil moisture, probe depth, and plant interactions with the soil. Additionally, testing soil runoff, as many home gardeners do, does not give an accurate picture of soil pH, as it can be affected by dilution rate, among other factors. We also do not recommend testing the pH by placing the probe directly in the soil. The pH adjustors present in the soil, such as oyster shell and dolomite lime will not register on the meter since they are activated once the come in contact with water. [/FONT]
[FONT=&]In order to have a clearer picture of soil pH we recommend running a soil slurry test. [/FONT]
In the words of Billy Pilgrim, "So it goes."
PH rises and falls constantly, and is influenced by many factors. However, unless something is wrong to begin with, I doubt the changes will push the ph into a state thats too low or high.
Start with good medium and good water and off you go. But just if the wheels start coming off and you can't resist putzing around with it I agree with Trapper. The Accurate 8 is the way to go. Runoff water is a chaotic brew gathered at a chaotic moment. FWIW customer support people at Fox Farm, General Hydroponics, and Sunshine Advanced say runoff water is NOT a good gauge of what's going on at the roots. I got this from Fox Farm:
[FONT=&]Accurately testing soil pH requires expensive lab equipment that is not available to most home gardeners. Soil pH testers purchased at your local garden center can give variable readings based on soil moisture, probe depth, and plant interactions with the soil. Additionally, testing soil runoff, as many home gardeners do, does not give an accurate picture of soil pH, as it can be affected by dilution rate, among other factors. We also do not recommend testing the pH by placing the probe directly in the soil. The pH adjustors present in the soil, such as oyster shell and dolomite lime will not register on the meter since they are activated once the come in contact with water. [/FONT]
[FONT=&]In order to have a clearer picture of soil pH we recommend running a soil slurry test. [/FONT]
In the words of Billy Pilgrim, "So it goes."
Yes, its name is Accurate 8, and they run ~$50-60 in the US. If you use it to test bag soil pH, you'll either need to water a small pot of it, then test that (soil pH will always be higher when dry, and dry soil will throw off the readings), or do the "soil slurry" test mentioned previously. I pot up every new bag of soil, water it and test it. With Fox Farm Ocean Forest soil, it has saved me from a lot of headaches, as their pH from bag to bag, can fluctuate significantly.
