Lifting pots to determine weight, as a method of telling when it's time to water, is only useful if you can actually lift the pot. There are other variables that can interfere, as well. Not all pots, plants, or mediums are of equal weight, and there's really no accurate way to measure moisture content within the root/soil ball using this method. Just because a pot weighs less today than it did yesterday does not mean it needs more moisture added... some soils will retain moisture at the very center and still feel light when we lift that pot. Using a finger to test for moisture is not accurate, either. Human fingers are not long enough to reach down into the center of most pots, therefore, we cannot actually determine how much moisture by touch the lower portion of the soil ball contains. Just because the top couple of inches are dry to the touch, does not mean the rest of the root/soil ball is dry. The human sense of touch doesn't usually detect any moisture in vapor form, either... so there's a good possibility that there's still moisture left when many people think they feel dry medium. In my own experience, moisture meters aren't very accurate, either. They detect water by measuring electrical conductivity, or something to that effect... I'm not an expert on electricity... but I have found that most meters on the market are way less than accurate. (Perhaps someone with more knowledge can explain moisture meters and how they work.) Wooden skewers are, to date, the most accurate method I've found for testing moisture levels within the root/soil ball of my containerized plantings. It works every time!

It's tough figuring out what is the best solution would be. Personally, I would probably just get a ph testing kit at a home depot - it costs just a few dollars, and once your ph is set, it doesn't change very often (unless you add something to the soil). As far as as moisture, I use this soil moisture meter. It has worked well for me as it was in the Goldilocks zone for prices. Rather than costing $2000 as a professional piece of technology, it cost about 80. And it's not like the cheap ones, in that salinity/fertilizer doesn't affect it. As far as light, not sure what to say. It is obviously very crucial to a plant's growth and I know that certain colors of light are more essential than others, but I don't know of an affordable device that works well. Honestly, I think that the natural light of the sun makes the most sense...

Raspberryflyer, I will be more polite and diplomatic in my answer... I just bought a PH meter for my daughter who is doing a science project concerning the acidity of soil. It's not an expensive model ($15.00 Canadian) and we were told it may not be accurate, but so far it's giving the readings which I expected. Dipped in vinegar which is highly acidic, the meter registers in the deep of the lower PH levels, and dipped in mucky ashes from the wood stove, the meter goes straight to the higher PH levels. So far we've tested potting soil, forest soil, garden soil, lawn soil, etc. and the readings are what I expected them to be. It appears to be working well. It's a simple meter with two prongs which are inserted into the muddy soil. In essence, you place the soil in a bottle, add water to make it muddy, then insert the meter and wait about 60 seconds. We kept the receipt just in case it didn't work, so you might want to do the same. It was bought at a garden center. Since the ground has started to freeze here, we were out on Sunday with a pick axe digging. You have to get soil from about 5 inches down. I am actually glad she chose this as her project this year. I have been wanting to buy such a meter for some time, and this gave me the right excuse. I have places on the property where blueberries grow and so I wish to keep the acidity at a high level. In the ornamental gardens, I'm looking for neutral soil. This meter will help me in achieving these goals. I truly hope I've helped in answering your question, and that you will not be discouraged from posting at this forum in the future due to the above response. Most folks here are kind in nature and quite helpful and do actually focus on the question at hand. Sincerely, Nicole.

You're meter will work just fine since soil pH is just a measurement of the pH in the soil solution anyway. What you do is make a saturated paste. You put your soil into a container and slowly add D.I. water and mix it in until it is fully, but not overly saturated. Saturate the soil until (I know this sounds goofy) it has a consistency pretty close to a Frosty from Wendy's. Then add a few more drops and mix until you get a tiny meniscus (for lack of a better term) of water along the bottom edge of your soil blob when you tip the container at an angle. Then you need to let it sit for a minimum of 8 hours. 24 is better. Cover the container with aluminum foil to keep water from evaporating. When you take off the foil, there will be a little bit of free water pooling on top. Don't sweat it, that's normal, just mix it back in. If you're in a lab, I'm assuming you have a Buchner funnel and an Erlenmeyer flask you can hook up to suction. If you do, set it up and throw some filter paper in the funnel and suck out the moisture. Then run your pH on the leachate.