Two typical areas of concern about using chemicals in the garden are contamination of food & the ground water.
A natural concern of many people is the use of mineral nutrients from commercial sources in their vegetable gardens.
They want to know if minerals would, or even
1) contaminate the food they eat or cause other problems, or
2) cause a toxic build-up in the soil and leach into the groundwater, eventually adding to the problems we have in our streams, rivers, and oceans.
We have the answer to those concerns.
1) Plants fed with mineral nutrients constitute 90+% of our food supply in the United States, and higher than that in the Netherlands, which has the healthiest population in the world. Rather than minerals being a potential health problem, using organic materials to feed plants has several drawbacks and potential health hazards.
Most manure and compost has not been sterilized, and therefore can have diseases, bugs, and weed seeds in it, which will flourish in your garden and substantially reduce your yield. In addition, there is some risk of people getting infected from something that’s toxic to humans as well, such as the ultimate killer Mad Cow Disease. Unsterilized manure and compost have been blamed for numerous cases of salmonella and E-coli poisoning recently, and have caused the recall of millions of dollars worth of vegetables. Organic buyer beware!
Unless the organic material HAS been composted very efficiently in an aerobic process, which is very rare and requires sustained temperatures of 140+ for several weeks, you run the risk of the aforementioned problems.
In addition to the foregoing, you may get much lower nutritional value in your vegetables. This is because you do not know what or how much you are feeding your plants, since every batch of manure or compost is different, and because none of them have been analyzed to determine their nutrient content. You can expect the manure to have much LESS nutrition than the original plant contained because of going through the cow, then sitting in a compost pile for months in the rain and snow.
Because we use mineral nutrients in our gardens and wanted to be CERTAIN we were not contributing to any toxicity problems, in 1998 Dr. Mittleider and I hired two highly respected soil labs to perform extensive tests for us regarding this very question. The two labs were Stukenholtz Labs, in Twin Falls, Idaho, and the Brigham Young University Soil Testing Lab, in Provo, Utah.
Under supervision, and according to specific instructions from the labs, we drilled holes for 45 tests. Three gardens were tested for build-up of fertilizer salts. Test cores were used at 1′, 2′, and 3′ depths in each hole.
One garden was Dr. Mittleider’s own backyard garden, which had been used for 21 years at that time; the second location was my garden at Utah’s Hogle Zoo, which had been used for 10 years; and the third garden was a very visible large garden 20 miles South of Salt Lake City at a place called Thanksgiving Point, which had been in use for 4 years.
The test results came back showing there was NO toxic build-up of salts in ANY of the test sites. There was NO indication of ANY fertilizer being flushed into waste-water systems. And some of the test holes even had LOWER salt levels than the controls, which were taken from non-fertilized aisles and garden periphery.
This did not surprise us (although it surely did surprise a couple of people who had suggested we were polluting the ground water), because we use very little mineral salts, and we spread their application over the growing season, instead of applying them all at once, as those who apply manure and compost most often do.
We only apply 7 ounces of fertilizer salts to about 3,300# of soil, and do it every 7 days only 4 to 8 times for most crops. Ever-bearing crops will usually receive 10 to 12 applications, spread over several months.
Compare this to the many POUNDS of fertilizer salts organic growers apply to their gardens ALL AT ONCE before planting. That concentrated one-time application is much more likely to cause run-off or seepage into the groundwater than the small amounts the Mittleider gardener applies. And quite often emerging seedlings are stunted or killed by the heavy concentration of fertilizer salts from the manure as well.
Our vegetables are healthier, because they receive their nutrition throughout the season, as they need it. And BECAUSE they are very healthy, they are less susceptible to problems from diseases and pests. They also have fewer problems with pests and diseases because they spend less time in the garden before being harvested. As an example I’ve grown 82-day corn to maturity in 61 days.