Don't guess--soil test
By Tracey Payton Miller
OSU Horticulture Educator
Now is a great time to test your soil. Not only will you be proactive in the landscape, but you can get some dirt therapy while you're at it.
I cannot stress soil testing enough. If you ever fertilize you must test your soil regularly. Those of you who are purely organic or only use compost are not exempt. Norman is a very green community; there is no excuse for a "shot in the dark" approach to fertilizing. This time of year, the testing lab isn't as bombarded with soil, and testing now gives you time to educate yourself and develop a plan.
Unless you live in a bubble, you know we are and have been in a severe drought the past several years. I urge you to be smart about your water usage in the landscape, whether using city or well water. Forgo watering at any point if you can. But also, if you applied fertilizer last year, there may be fertilizer yet to be used in the soil. Without adequate moisture, fertilizer is not used by the plant. The only way to know if you have excess nutrients is to soil test.
If we continue with the current drought conditions, do not apply fertilizer. This is a sure way to stress your lawn, garden, or trees even more than they currently are. Do not fertilize after a small rain event either, there must be adequate moisture throughout the soil profile.
Timing fertilization with a rain event is a common practice. However, it could exacerbate the problem. This is because Oklahoma rarely gets a nice, calm shower. We may receive an inadequate sprinkle, or a gully washer. Only after the drought recedes, water a small amount after applying fertilizer to incorporate it into the soil. This will tend to lower or eliminate the amount of nutrients entering the water system.
Now that I've scared you into doing a soil test, you need to know how to do it. I recommend testing each area of the landscape differently. For example, the lawn should be tested separately from the vegetable garden, or flower beds. In addition, you may choose to test the front yard separately from the back yard, especially if you have different species of turf growing in those areas. Keep in mind, each sample you submit may have varying recommendations and methods of fertilization.
A routine soil tests consist of 15-20 random samples per location. The more samples you take, the more representative it is and your results will be more accurate. Each area you sample, go 6" to 8" down and include all of the depth in the sample. You can use a shovel or hand trowel to retrieve the soil, or soil probes may be available for check out from your closest Extension office. Eliminate any mulch, rocks, or plant material from the sample. You may choose to gather all the soil together in a bucket, and then mix the soil together thoroughly. Bring three cups of the mixture to your local extension office. I recommend a routine soil sample, which costs $10. Talk to your local extension educator if you have questions about testing. The OSU Soil, Water, and Forage Analytical Laboratory does not test for residual pesticides. More information can be found at http://www.soiltesting.okstate.edu/pricelist.htm.