We know that the warm weather garden season is going to come to a close at some point. The question is just a matter of when. Three years ago, we had our first freeze on October 18^th. If we were to repeat that year, the summer growing season would have been over yesterday. Last year, our first freeze date was November 22^nd. So, the timing varies, but we know it’s coming. We also know it’s coming if we look around our gardens. Our annuals look tired, kind of like we feel. At this point we are just continuing to help them along, knowing that the end is coming.

In contrast to this somewhat sad trajectory, if you are like most gardeners, we are already thinking about next year. We’re thinking about how we might approach things differently. In the midst of all this thinking and planning, there is one thing we can do to help us be better prepared for next year’s growing season. That one thing is getting our soil tested. Why is it good to get our soil tested at toward the end of the summer season? Here’s why.

For the most part, we are primarily concerned with the three primary nutrients found in our soil: nitrogen, phosphorus, and potassium. When you shop for fertilizers, the bags will have 3 numbers on the bag such as 19-19-19. This tells us that this particular fertilizer is 19% nitrogen, 19% phosphorus, and 19% potassium. Of these nutrients, nitrogen is considered a mobile nutrient while phosphorus and potassium are considered immobile nutrients.

This means that when you sprinkle nitrogen fertilizer on the soil, it dissolves and spreads easily through the soil. In contrast, phosphorus and potassium don’t easily move through the soil. Because of this, adjustments to nutrient levels of nitrogen are pretty easy and quick. But changes after applying phosphorus and potassium take a while longer for these nutrients to move in the soil and become available to your plants. So, when we do a soil test in the fall, if there are adjustments that need to be made to these immobile nutrients, we can get those nutrients into the soil now, giving them all winter to get where they need to be…so to speak. This way they will be available to your plants in the spring. Fortunately, it’s pretty easy to get your soil tested.

First of all, you need to collect your soil sample. To do this you are going to need a bucket and a collection tool. This collection tool can be a trowel or a bulb planter. We have soil collection tools available for check out if you would like, but it’s not necessary.

When you have your tools, you will need to collect about 15 to 20 samples from the area you want tested. We get this many samples because it makes the results more accurate.

When you are collecting your samples, be sure to dig down 6 inches because the test is calibrated for a six-inch depth. As you collect these samples, drop them in a bucket. After you collect them all from the sampled area (this could be your garden or your yard) mix them up in the bucket, remove the sticks etc., and fill up a sandwich bag with your collected soil mix.

When you have your sample, bring it to the Tulsa County OSU Extension at 4116 E. 15^th Street here in Tulsa. You will need to fill out a form and pay the $15 fee for testing. We will send the sample to the OSU soil lab, and you should get your results back in a couple of weeks.

When you fill out the form, indicate where your sample was collected. Was it your yard or your vegetable garden or your flower garden etc. Where the soil came from can make a difference in the recommendation you will receive on which nutrients you need to amend or not amend.

Once you get your results/recommendation back, you will be able to make those corrections, which will give your soil time to get adjusted and ready for your spring garden giving you a bit of a head start. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Tom Ingram