Should We Be Garden Soil Testing?
You’re darn right we should! And, I am going to tell you how to get it done! In this post you will learn about preparing soil for a vegetable garden and the importance of home garden soil testing. But, before we delve into the nitty gritty, you first have to understand the medium you will be using…DIRT !!!
Dirt…what is it…and what’s it good for?
Dirt, or soil, is made up of sand, silt, and clay. The amount of each determines texture. The dirt will have soft areas of small, loose, crumbly stuff as well as harder dirt balls. My BENGAY-covered back is evidence that there is also the more-than-occasional rock to remove. Add in some space for critters, water, and air to move around and, make it any color from deep maroon to brown to black.
The dirt I shoveled as a young-un was as black as you can get. It was nutrient rich and the pH would normally stay in the ideal growing zone with just a touch of limestone (to raise the pH a bit) and fertilizer (normally 10-10-10). It wasn’t rocket science to keep our soil healthy and producing great vegetables.
Rich dirt in The Days of Old…
Having rich dirt was a blessing because, even though we did an occasional pH test with litmus paper, it was next to impossible to get soil testing done for nutrients…at least where we were living.
But, these days, in many parts of the good old U.S.A., the soil seems to be somewhat over stressed and worn out…exposed to a host of man-made contaminations…chemical…biological…too much clay (normally the culprit for insufficient water drainage…lack of crop rotation (a discussion for a future post)…and the list goes on.
There is good news…with all the soil test kits on the market and the easy availability of having soil testing done through county agricultural extension services, it’s a no-brainer.
Do a Soil Test.
Take soil samples from about a half-dozen random areas in your garden (more if you have a larger garden). If you’re like me, you’ll end up with more than a bucketful.
Clear away the surface dirt and, with a shovel or trowel, take a dirt sample at least 4 inches below the surface.
Dry it out. Stir it up to blend it all together. Take out the rocks, twigs, and weeds…and, pour it through a sieve so you will have fine, dry dirt with no lumps or vegetation. Take about a quart of dirt in a plastic baggie to your county cooperative extension office.
At the extension office, they will normally transfer the dirt they need for the test into a special paper bag labeled with your contact information and send it off to a local university for lab testing. The cost for the soil test is nominal…usually less than $10, which is about half the price of the premium soil test kits and you will get detailed results…with recommendations on what type fertilizer and/or limestone you need to make your dirt healthy.
Here are results from soil testing my home vegetable garden.
The nutrients listed are needed at the levels recommended on the graphs to help insure a successful year of vegetables in my garden.
pH Ranges for a Few Vegetables and Fruits:
|Vegetable||pH Range||Vegetable||pH Range||Vegetable||pH Range|
|Asparagus||6.0 – 8.0||Corn||5.5 – 7.5||Potatoes||4.8 – 6.5|
|Beans||6.0 – 7.0||Cucumbers||5.5 – 7.0||Sweet Potatoes||5.2 – 6.0|
|Beets||6.5 – 8.0||Eggplant||5.5 – 6.5||Radishes||6.0 – 7.0|
|Broccoli||6.0 – 7.0||Lettuce||6.0 – 7.0||Rhubarb||5.5 – 7.0|
|Cabbage||6.0 – 7.5||Onions||6.0 – 7.0||Spinach||6.0 – 7.5|
|Cantaloupe||6.0 – 7.5||Peas||6.0 – 7.5||Squash||6.0 – 7.0|
|Carrots||5.5 – 7.0||Peppers||5.5 – 7.0||Tomatoes||5.5 – 7.5|
|Fruit||pH Range||Fruit||pH Range||Fruit||pH Range|
|Apple||5.5 – 6.5||Pear, common||6.5 – 7.5||Raspberry, red||6.0 – 7.5|
|Blueberry, high bush||4.5 – 5.5||Plum, American||6.5 – 8.5||Strawberry||5.5 – 6.5|
|Cherry, sweet||6.5 – 8.0||Raspberry, black||5.5 – 7.0||Grapes||5.5 – 7.0|
As shown on the Soil Test, the Phosphorus (P), Calcium (Ca), Magnesium (Mg), and Zinc (Zn) levels look pretty good but, I need a bit more Potassium (K). You can see that my pH level is low (5.8). The overall recommendation for a home vegetable garden is a pH between 6.0 and 6.5…a good range in which most of your vegetables will thrive.
“Neutral pH” is 7.0. A garden with a pH lower than 7.0 is acidic and plants may not be able to absorb vital nutrients like calcium, magnesium and phosphorus. A pH higher than 7.0 is alkaline and plants may have a problem soaking up zinc and copper, among other things.
Adding limestone makes the dirt more alkaline.
Adding sphagnum peat, for small gardens, or acidifying fertilizer, for larger gardens, makes the dirt more acidic. If you have container plants, mix 2 tablespoons of vinegar to a gallon of water and water the plants several times over a week to increase the acidity.
At the risk of getting too technical, pH is the scientific abbreviation for “potential of Hydrogen” or, the measure of acidity or alkalinity of a solution or material.
The soil testing done recommended spreading 20 pounds of 16-4-8 fertilizer for every 1,000 square feet of garden space. If your garden if 500 square feet, you would use 10 pounds. If your garden is 2,000 square feet, use 40 pounds.
The numbers on the Soil Test, 16-4-8, refer to the amount of Nitrogen (N), Phosphorus (P), and Potassium (K) in the fertilizer. It calls for a fertilizer containing 16% Nitrogen, 4% Phosphorous, and 8% Potassium.
Nitrogen is crucial as a key part of chlorophyll, needed for plant photosynthesis.
Do the soil testing. Enjoy the harvest. You will never regret it!
Can you see how important it is to know what your garden soil is composed of? Do you soil test your garden plot? If so, you use a purchased kit…or, do you get an itemized soil test from your county agricultural cooperative? Comment below or email me: firstname.lastname@example.org.
Now…let’s get…Down & Dirty !!!