Soil Testing: The Key to Better Vegetables

assorted vegetables

Most gardeners hear of soil testing and understand that good soil is a living thing, teeming with micro-organic life, essential to plants.
They are also usually aware that soil organisms need air, so they keep their soil in good tilth (soil that has the proper structure and nutrients to grow healthy crops) to allow air to enter.

Water, of course, is necessary at this point to dissolve useable nutrients, as plants all live on a liquid diet.

Science has demonstrated that the only way we can overcome man-made pollution of our soil, is to turn to modern methods of control. Improving soil quality is an ongoing process. The key to this control is the soil pH, the acid-alkaline balance of the soil. The only way we can intelligently determine pH is by testing.

Average “Gardener” Indifferent to Soil Testing?

It is difficult to understand the average gardener’s indifference to soil testing. Those who have taken our modern scientific advancements in stride, accepted the automobile, airplane, radio and television computers, cell phones, modern medicines and vitamin pills, still go into their gardens and literally pour everything in the book on their soil without the faintest idea of what is needed – or how much.

Some, perhaps, do not realize that soil nutrients in over-supply can be more destructive to plant life than the lack of them. They merrily douse here and douse there saying “If a little is good – a lot is better!” Others apparently feel that soil testing is just another gimmick, unessential, merely another attempt to fatten someone’s pocketbook. Nothing could be further from the truth.

Commercial growers who depend upon production for a living spend thousands of dollars annually testing, correcting and maintaining constant pH control. It their crop insurance with pH testing. They do it because it means greater yield and better quality – exactly what the home gardener is after.

The only chemical formula we will consider is H2O (water), so that you may understand how it influences soil pH. When water enters the soil, a small portion of it ionizes and H2O becomes H (hydrogen ion) and OH (hydroxyl ion).

These ionized water ions unite actively with plant food elements and the degree of acid-alkaline balance is in direct proportion to the relative amounts of H and OH ions present. Hydrogen ions produce acidity – hydroxyl ions, alkalinity.

The Soil Testing pH Scale

In soil testing, a mathematical scale has been established to indicate relative pH (potential hydrogen). The figure 7 is designated as the neutral point where acid and alkali are in exact balance.

Soils testing below 7 are increasingly acid as the figure decreases; readings above 7 are increasingly alkaline as the figure increases.

One Point Makes A Difference

When you consult a vegetable pH preference list and find that beets and carrots prefer a pH of 7.5, while chives and radishes need a pH of 6.5, don’t raise your eyebrows and say, “What possible difference could one point make?”

Keep in mind that each point of the pH scale indicates a redoubled quantity; that 6 indicates twice the acid of 7 and 5 indicates 4X times the acid of 7. The same ratio applies to the alkaline scale. So, even a half point can mean a wide variance in soil balance.

The pH preference of most fruits and vegetables is as follows:

pH 7.5 apple, artichoke, asparagus, beet, cabbage, carrot, cauliflower, celery, lettuce, onion, parsley and plum.

pH 6.5 broccoli, brussels sprouts, cantaloup, cherries, chicory, chives, corn, crab apple, cucumber, eggplant, endive, garlic, horse-radish, kale, kohlrabi, leek, lima beans, mushrooms, muskmelon, okra, peach, pear, pea, quince, radish, rape, raspberry, rhubarb, rutabaga, salsify, soybean, spinach, swiss chard, water cress and watermelon.

pH 6 apple, bean, blackberry, buckwheat, cowpea, currant, gooseberry, lentil, peanut, pepper, sorghum, squash, strawberry, tomato and turnip.

pH 5.5 grape, parsnip, pineapple, potato, sweet potato and pumpkin.

pH 4.5 blueberry and cranberry.

Better Quality Veggies, Fruits & Berries

carrots at farmers market
Within the indicated ranges, nutrients and micro-organisms essential to the noted plants are found in best supply and most active conditions. This is more vitally important to food plants than to ornamentals.

In order to have fine quality vegetables, fruits and berries, there must be no growth lag, the chief cause of woody root crops and runty, tasteless bush and vine crops.

In addition to improved quality and quantity, a sustained testing program brings extra benefits. Soil tilth (crumb structure) is more easily maintained within a pH 6 to pH 8 range, with a resulting larger population of soil organisms.

This means more available plant nutrients. It also prevents lock-up of important trace elements. In this way, you save money, as you need apply smaller amounts of fertilizers and soil supplements, and water less often. Yet you will produce higher vitamin content in the foods.

Considering the vast difference in soils from east to west and from north to south, it is obviously impossible to recommend specific corrective measures for any one area.

The solution to any soil imbalance should be taken to your favorite nursery authority or garden center. Your local supplier has the correctly compounded fertilizers and supplements for your area. We do not hesitate to have a family counselor, be it doctor or attorney; why not a soil counselor?

Simple Soil Testing Equipment

Now as to the necessary equipment for soil testing. A great many gardeners, both professional and amateur, have turned to the home soil test kits. These have no involved mathematical equations to work out; no knowledge of chemistry is needed.

Soil pH, nitrogen, phosphate and potash needs are usually determined by a color comparison of the test sample, with a color card supplied in the kit.

You will find that soil constantly changes, both in pH and in nutrient needs; therefore tests should be made at least four times a year. Even in a large area, about four hours work per season will accomplish these tests. Balance those hours against the savings in dollars and disappointment, and you will probably conclude that soil testing is a practical modern tool in vegetable gardening.

Images: Augapfel | John-Morgan

Tips To Improve Your Plant Care
Sign Up For My Free Daily Newsletter

We will never share your email address period.

{ 0 comments… add one now }