I want to know not only the amounts of nitrogen, phosphorus, and potassium (the NPK of the fertilizer labels), but also the micronutrients boron, manganese, zinc, copper, iron, and sulfur. In addition I’ll look at the soil pH and the amounts of calcium and magnesium which affect the availability of the other nutrients for uptake by the plants. The report gives other useful information that I won’t go into here.

If I were starting a home garden, particularly in an urban area, I would pay particular attention to the amount of lead reported by the testing lab. Leafy greens such as spinach are well known to take up lead & other heavy metals from the soil.

There is a strategy to taking a soil sample. You want your sample to be representative of the entire field and you want to sample where the roots are taking nutrients from the soil. You accomplish this by taking a dozen samples scattered across the field and blending all the samples together. All the samples are collected the same way and depth, in our case about 8 or 9 inches.

You can sample with a shovel, digging a dozen pits in your field, slicing out a slab, cutting out a vertical slice of each slab, and blending the 12 slices together. In your backyard, this is a reasonable thing to do. However, if you want to sample a number of fields, this can add up to a lot of work.

I chose to invest $100 in a tool that greatly reduces the workload, and also probably gives a more consistent sample than I could get using a shovel.

A soil sampling probe, a bucket, and a trowel are the kit for collecting soil samples for testing.

I bought my probe years ago, probably  from Peaceful Valley. This is something of a deluxe model, 3 foot long, with a foot step. Both reduce the effort and bending required to collect a sample. A bucket for collecting and carrying the samples and a trowel to break up and thoroughly mix the samples completes the kit. Sometimes I take along a screwdriver to help poke soil out of the probe tip. It is important the the tools be stainless steel or plastic. Rust rubbed off a rusty trowel will throw off the iron analysis.

In this closer view you can see the sample of the top eight inches of soil still held by the soil sampling probe.

With the probe, the sample collection goes quickly. Push the probe into the ground with a twist. Carefully pull the probe back out. Take a moment and examine the soil. Can you see different layers? Is there plenty of organic matter? Do samples from different areas look different? Dump the sample into your bucket and go on to the next spot.

I send my soil samples to the UMass Soil Lab for analysis. There are plenty of other testing labs that you can deal with. Due to variations in the test methods, there is apparently significant variation in exact details from lab to lab, although they should all give similar recommendations. If you do want monitor the effects of your management strategies by looking for trends from year to year, then it is important that you always use the same lab.

You can purchase do-it-yourself test kits for pH and for NPK. I don’t have any experience with soil test kits. The lab tests gives so much more information at a modest cost that I’m happy to wait for the lab to do the test for me.

I got my test results in the mail a few days ago. I sent them off to Walt, at Walt’s Organic Fertilizer in Ballard, for Walt’s suggestions for this year.