Making sense of soil tests

Q: Can you help me understand my soil test results? I’m having a terrible time with blight on my tomatoes, and I need to know what to do.

— Judy from Salem

A: Anytime you get your soil tested, be sure the company is going to give you a summary report along with recommendations. But sometimes the results are difficult to understand.

There are some key points to be sure you understand and use to correct soil issues. Correcting issues based on a soil test an improve plant health but cannot prevent disease.

Soil testing is an excellent measure of soil fertility. It is a very inexpensive way of maintaining good plant health.

A standard soil test provides the status of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), pH, cation exchange capacity, lime requirement index and base saturation.

To many of you, this may sound like too much information. But don’t worry. We can help you interpret these results and the recommendations which should come with these results. With a representative soil sample and an accurate test, sound fertilizer recommendations can help you improve plant quality and productivity, and save money, too.

In general, Judy’s soil test results will help her to be sure her soil has the proper pH and nutrient levels to grow great tomatoes.

But what the soil test will not provide is any measure of disease in the soil or how to prevent the disease. This disease lives in the soil and affects our tomatoes to some degree every year. Judy is like most of us. We fight early blight on tomatoes every time we grow tomatoes.

This year was a stellar year for early blight and Septoria leaf blight, causing plants to yellow and lose their leaves.

In general, the answer to early blight is not just spraying to keep the disease at bay. In fact, spraying correctly is quite a challenge for home gardeners and must be attended to on a regular basis. Thus, we recommend it as a last resort.

Cultural practices are a better way to start. Early blight and septoria are soil borne diseases. Thus, if we can keep soil from splashing on the plant leaves, we can reduce infection. Mulching (usually with flat newspapers, then some kind of mulch on top of them), will go a long way in reducing the splashing of soil onto the leaves.

Proper staking, distance between plants and sometimes pruning of lower leaves will help reduce leaf wetness and the chance of infection as well.

To learn more about early blight (and to develop your plan for next year’s tomatoes), go to http://go.osu.edu/earlyblight. To learn more about soil testing through OSU Extension, visit http://go.osu.edu/soiltesting.

Barrett is the Ohio State University Extension educator for agriculture and natural resources in Mahoning County. Call 330-533-5538 to submit questions to the Plant and Pest Clinic.


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