Flint on Crops: pHinding the Right Balance Between Acidity, Alkalinity

    At least you have gotten past the title to read this first sentence. I’m talking about one of the most under-appreciated factors in nature.

    What pH really is: the negative base ten logarithm of the hydrogen ion concentration of whatever material you might want to know this about. That may be plain water, rainwater, a chemical solution, soil, or any one of thousands of other things.

    As one of my professors used to say, let’s dumb it down so those with little or no background in chemistry can find a handhold on it.

    The value we refer to as pH is a measure of the balance between acidity and alkalinity. The low end of the scale from 0 to 7.0 is the acidic side of the balance and the high end of the scale from pH 7.0 up to 14.0 is alkaline. At pH 7.0 we say the solution is “neutral.”

    We seldom see anything we work with in agriculture get outside a range from 4 on the low side to 9 on the high side. Outside these limits there are very few organisms or solutions that can remain unaltered. Most farmers are familiar with pH as it pertains to soil, and we know that in most cases the crops we grow perform best between pH 5.8 up to 6.8.  Some “experts” may want to widen this range while some may want narrow it, and they may be right.

    We could discuss this all day, but it would come down to the fact that this is the “sweet spot” where most of the nutrients that plants need are available for uptake and use by the crop. When we get down to about soil pH 5.5, the acids begin to draw in toxic elements like aluminum and manganese that can retard root development and suppress normal organic activity in the soil.

    And when we get above about 7.5 or so there is not enough acidity to keep nutrients in solution, so plants can’t get them there either. So, keep the soil within this range so crops can get the nutrients they need. If the soil were a running engine, which it is in a sense, this is where the fuel mix is about right. If you could hear it you would say it’s “purring.”

    Most of our soils in the South are naturally acidic. It seems strange that there are regions where soil pH is alkaline. We have isolated “sodic” soil areas that have high soil pH levels in this region.

    But for us the main pH concern is keeping the reading around or just above 6.0, and we normally do that with agricultural lime. There are other products like basic slag, ash, and byproduct lime from water treatment and other processes.

    We also need to consider pH when it comes to spray solutions.  Many of the products we use perform best when the solution pH is below 6.0. Much of the water we pump from wells in this region is above pH 7, and I have seen some as high as pH 9.

    While a few products work without adjusting (buffering) the pH down below 6.0, it’s a fair assumption that a pH buffer is a good idea when mixing expensive products. Some of them, especially some of the more popular glyphosate formulations have a pH buffer formulated into the product so you may need to have a pH meter to check the solution.

    In a worst case scenario, a pH sensitive material may lose enough of its effectiveness to produce poor results by the time you drive from the mixing area to the field. There are a few products that are very pH sensitive and perform best at pH levels as low as 4.5 or so.

    This is something you need to get familiar with because there is no sense paying big bucks for products only to mix them with alkaline water and have them fail to perform. You stand to lose not only the cost of the material but also valuable yield as the results of failure to control insects and diseases.

    I’m pHinished with that. Happy New Year.




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