Nutritional needs for turf are different than for flowers or vegetables. With a clean bucket and shovel, dig down 6 to 8 inches in the area you need tested. Put about a cup full of soil from the bottom of the hole into your bucket. Do this in about nine other spots spread out around the garden area. Mix the soil together, then let it dry by laying it out on a sheet of newspaper for a few days.
Gardeners can look to their local extension offices for advice.
They have a list of many labs, some in state and others out of state. The labs can test things such as soil, soilless mix, plant tissue, feed, manure, compost, sludge, nutrient solutions and water. Your extension office will be able to give you a copy of this list and instructions on the proper way to collect a sample for testing. You can also take a less-scientific test of your own. Combine a tablespoon of dried garden soil with a few drops of vinegar.