Gather samples at the same point in the watering/fertilizing cycle for a crop. Sampling an hour after the last water/fertilizer application represents nutrition of the soil solution well. Be consistent.
Problem crops or benches should be sampled individually. Include samples from good and bad plants where visual symptoms are evident to compare nutrition differences.
For routine analysis, samples should be collected from 5 to 10 containers, depending on container size, and combined into a single sample. The sample should be collected by either: a) removing a wedged- shaped piece from the top to the bottom of the pot, excluding the top and bottom one- half inch of the substrate or b) pinch a handful of substrate from the center one-third of the pot. Include the entire soil volume when sampling from plug flats excluding the top one-eighth of the medium.
Thoroughly mix the samples to make a single homogeneous sample. The sample to be tested should be at least one pint of media. Remove any large roots or debris and avoid including any slow-release fertilizer or lime in the sample.
Air dry the samples and send to the lab as soon as possible. If samples cannot be mailed immediately, they can be refrigerated.
Samples should be placed in a new plastic bag or container labeled with your name or company name and a sample identification that corresponds to the ID on the submission form.
Follow the same procedure every time you sample so you can compare results and detect trends over time.
One to 2 pints of potting media are required for conducting analysis; smaller volumes can be submitted, but the results may not be as accurate
New potting medium should be wetted to container capacity by placing the sample in a growing container, watering it until drainage occurs, and allowing it to stand for a few days. The sample can then be collected and mailed. With mail delivery time, this allows about a week for the lime to react and correct pH readings to be obtained.