SDSU Extension checked home kits against laboratory results on five soils running from pH 5.8 to 8.1, and for the most part the kits came within one pH unit. That is close enough to act on in a home bed. Garden soil pH testing comes down to two steps. Pull one composite sample from the bed you care about, then read it with a capsule kit, a test strip or a meter. The sampling half is where the error creeps in, and it is the half people rush.
One scoop tells you about one spot, and beds are seldom that even. Old amendments and foot traffic leave their mark in patches, so the corner by the gate can read nothing like the middle of the row. Take a spread of small cores across the whole bed and blend them into one sample instead. The average of the bed is the number you will be treating, so that is the number worth measuring.
Walk the bed and pull 8 to 10 small cores, each one 6 to 8 inches (15 to 20 cm) deep, spread across the whole area rather than clustered in one end.
Tip every core into a plastic bucket and stir until the color runs the same all through. That blend is the sample you test.
Follow the kit or laboratory instructions on soil amount, water amount and wait time. Shift the ratio and you shift the result.
Match the color in good daylight, not under a warm indoor bulb. With a meter, let the number settle before you write it down.
Test each area on its own. The lawn, the vegetable rows and the blueberry corner each get their own bucket and their own reading, since one average across all three fits none of them. Prep matters as much as sampling here. A capsule kit hands you a set soil to water ratio and a set wait time, and changing either one moves the color you end up matching. Follow the measurements in the box rather than guessing at them.
A pH number means little without a target beside it. The ideal soil pH for vegetables runs 6.5 to 6.8, and most garden plants do best near 6.5. Blueberries are the exception and want 4.5 to 5.0, which is acid enough that a bed set up for tomatoes is the wrong home for them. Put your reading against the right range before you decide anything.
Any soil pH test kit answers the question most gardeners have. Does the bed sit in a reasonable margin for the crops grown, and is lime or sulfur needed? Between the formats, a meter has the edge on color strips. Judging a shade of pink against a printed chart is more subjective than reading a number off a screen, and two people can call the same strip two different ways. Strips still have a place, and I keep some around for a quick check. For a number I plan a season around, I want the meter.
Direction comes from the reading. Lime raises a low pH and sulfur lowers a high one, and neither works overnight. Plan on the sample you take now shaping the season ahead rather than next week's planting.
Leave the pH alone unless the reading sits well outside the crop's range. A bed at 6.3 under beans needs nothing done to it. A bed at 5.2 does. pH sets how much of the fertilizer you spread the plants can take up, so ground far off target wastes part of what you feed it. This is also where a home reading runs out of road. It says lime is needed without saying how much, while a laboratory adds a buffer test alongside the pH reading and gives back an actual lime rate for your soil.
Read the full article: Soil Test Kit: What It Gets Right and Wrong
