What to do with that soil test…

Have you tested your soil in preparation for next year’s garden?

The soil report you get back looks like a bunch of gibberish, right? Basically, your test will give you the results of pH, Phosphorus, Potassium, Calcium, Magnesium, Organic Matter, and CEC. Note: Phosphorus/Phosphate and Potassium/Potash are basically the same thing, so don’t let those terms confuse you.


You need a pH between 6 and 7 and a good blend of minerals for crops to grow well, so here’s how you fix things that are out of balance.

If pH is low, add lime. Lime takes a couple months to work in the soil, so don’t wait for Spring, add it now. To increase the pH by one, you need to add 40 lbs of lime per 1000 square feet. Yes, you’ll have to do some math. (And don’t ever think you’re done. My Tennessee soil tends to be on the acidic side, so no matter what I do, I still occasionally need to add lime. On a side note, pH is very, very seldom high. But if it is, add aluminum sulfate or sulfur. Lime and sulfur are both available at your local garden store.


One way to correct the Phosphorus and Potassium is to apply fertilizers. You know those three numbers on any fertilizer? Like 5-10-5 or 10-10-5? Those are Nitrogen-Phosphate-Potash. You can choose a single combination fertilizer with the correct ratios, or you can choose all different types and do the math specified on each package, or you can use nature’s way and apply good, organic material, and lots of it. Manure, peat moss, compost, etc. These will not only correct any deficiency you have, but will improve your soil, grow healthy organisms, and hold more water (see Organic matter below).


Calcium and Magnesium can be corrected with Dolomite Lime. It is a Calcium Bicarbonate like Tums. The difference between regular garden lime and Dolomite Lime is the Magnesium, so if your Magnesium levels are okay, the regular garden lime will add that Calcium into your soil, so no need to use two different limes.


As you may notice if you’ve had your soil tested in the Fall, labs generally don’t report on Nitrogen. If you do have a Nitrogen result, take it worth a grain of salt. Nitrogen moves very rapidly through the soil and it is near impossible to measure next Springs availability of Nitrogen during the Fall.

Organic matter:

This is the health of your soil as far as retaining moisture, aeration, worm poo, growing micro-organisms. Your lawn needs between 2 and 3. Your veggie garden would be better between 4 and 6. Again, add organic material: compost, manure, peat moss, mulch, etc.

Uh, CEC? What’s that?

CEC is Cation Exchange Capacity. It pretty much means how well your plants will grow (also taking into account the climate, weather, location, etc.) The lower the number, the lower amount of nutrients your soil can hold. The higher the number, the higher amount of nutrients. Think of it like the lowest number is probably sand. The next would be silt, then clay, and the highest number would be completely organic matter. To raise your CEC number, add lots and lots of organic matter. (I’m seeing a pattern here.) Mulch, shredded leaves, rabbit poo tea, lots of compost.

Hopefully, that gets you on the right track for a great garden next year.

A couple things to keep in mind:

First, different labs, states, counties, and towns calculate these items differently. In one county, your Potassium may be perfect, and the next county a mile away may say it’s low, so you need to always trust your gut and only let the numbers gently guide you.

Second, if you’re hooked on soil tests, the most important part is consistency. Always use the same procedure and the same lab. That way, you’ll know year after year if your efforts are working.

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