Soil PH & Nutrient Availability

pH is a numerical scale that runs from 0 (most acid) to 14 (most alkaline). 7, being in the middle, is neutral. For the last 20 or 30 years, the pH of soil has been rising. This is due to all of the granular generic blends in the Ag industry containing harmful chemical salts.

Most of the fertilizers that have been sold to farmers for the last 20 or 30 years, as well as the vast majority of fertilizers that are still being sold to farmers today, are chemical salt-based fertilizers. That means that in addition to the nitrogen, phosphorus and potassium, that bag of fertilizer also contains chemical salts. Did you know that potassium chloride is mined from underground salt beds that formed when ancient salt water seas evaporated?

The incidence of elevated soil pH has been increasing over the years. This would be all right if we could grow crops on alkaline (high pH) soils. But you already know that you can’t. Most crops do best in soil with a pH of about 6.5. Today it is not uncommon to have a pH reading as high as 8 or 9. Not only does the high pH limit your yields, it can also destroy the natural biological life already in your soil. When we first look at pH readings we might not think that the difference between a 6.5 reading and an 8.5 reading is very significant, but it is - 8.5 is 100 times more alkaline than 6.5.

Chemical Salt Fertilizers and Soil pH

The problem with adding too much chemical salt fertilizer to our soil is:

  • Injures the crop’s roots
  • Interferes with the normal life activities of beneficial soil microorganisms
  • High pH ties up nutrients that your crop requires to grow

As we have already stated, most crops perform best when the soil has a pH reading of about 6.5, and one of the reasons for this is the availability of nutrients. The majority of plant nutrients are most available to the plant when the soil has a pH of 6.5. Above that the availability of nutrients begins to decrease.

For example, the availability of Nitrogen begins to drop off sharply with a soil pH of 8. Iron, manganese, boron, copper and zinc also become less available as the soil pH rises from 6.5 to 8.5. Phosphorus, one of the primary nutrients, begins to be tied up as soon as the pH of the soil reaches 7.5.

We begin to understand the irony of using chemical salt-based fertilizer once we realize that when we add a traditional blend of fertilizer to a soil, with an elevated pH, the phosphorus almost immediately begins to be tied up in the soil, making it less available to our crops. The longer you continue to use chemical salt-based fertilizer, the more you have to keep using just so that there will be some phosphorus and nitrogen available. But the more you use, the more you have to use. Your soil also becomes more out-of-balance and the salts damage crop roots and beneficial micro-organisms in the soil.

As you can see, buying fertilizer can be very complicated. Although the label on the bag is correct, how much of the nitrogen and phosphorus remains available to our crops once the fertilizer is added to our soil can be totally different from what we thought we were being sold. You all know that it’s not the amount of fertilizer you put into your soil but the availability of this fertilizer to your growing crops that really counts.

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