pH Management

Thursday, October 27, 2016

Most of our newsletters have focused on nutrient management. However, pH management is also important providing clues as to why we may have nutritional and microbial imbalances in our soil. pH issues are difficult to diagnose until plant growth is impacted and no grower wants to discover that they have pH issues by plant symptoms. It’s important to acknowledge that pH readings give us no information as to why. pH is the result of elements in our soil, not the cause. Although it’s clear that many microbes can’t live at extreme pH levels.

A solution’s pH is a numerical rating of its acidity or alkalinity. All pH is measured on a logarithmic scale from zero (most acidic) to 14 (most alkaline, or basic); 7.0 is neutral. The pH scale is used by chemists to measure the concentration of reactive hydrogen ions (H+) in a solution. Most food crops prefer a pH of 6.0 to 6.5. Potatoes and most berries, which grow best in more acidic soil, are the main exceptions to the average preferred pH range. Soils too acid or alkaline make some nutrients unavailable to plants.

  • Below a pH of 6.0 (acid): Nutrients such as nitrogen, phosphorus, and potassium are less available.
  • Above a pH of 7.5 (very alkaline): Iron, manganese, and phosphorus are less available.

Synthetic chemical fertilizers — mainly those high in ammonium or sulfur — can make soil more acidic, as can tillage methods that reduce soil’s levels of organic matter. Reducing the use of chemical fertilizers, using more natural fertilizers derived directly from plant or animal sources can help build organic matter.  Adding organic matter is an indirect method of soil pH adjustment as it makes both acid and alkaline soils more neutral. Organic matter “buffers” soil against pH swings, especially sandy soil.  Plants grown in soil with a lot of organic matter have healthier roots. They’re able to extract enough nutrients from the soil even when the pH isn’t optimal. In a healthy soil with adequate organic matter, plants continue to grow at pH levels that would stunt growth in leaner soils. To make soil less acidic, materials rich in calcium (shrimp and crab exoskeletons/chitin) can be utilized.

Again, knowing the pH value doesn’t help us much with soil management decisions. For example, a high pH soils can be the result of sodium and potassium and no pH test reveals that. The reason we’re happy with a relatively neutral pH is that most nutrients, particularly the most essential nutrients, are most readily available to plants somewhere in the 6-7 pH range.

Growers commonly use lime to improve acidic soils but this destroys the microbes in the soil and doesn’t represent a long term solution. Andaman Ag offers products capable of stabilizing pH for optimal crop growth and quality including  Vermigrow Compost TeaAgrostim natural fertilizer, Aquasap(seaweed) and Pacific Gro Hydrolysate (chitin).

As always, I’m happy to talk more with you about our products and the benefits of sustainable and organic growing practices.