Friday, July 15, 2011
Chemical lawn fertilizers work well, for a while. However, the concentrations of chemicals that directly feed the roots bypass the soil biology. These fertilizers also contain salts, that when they come into contact with the soil’s countless number of microbes, cause osmotic shock – that is, water in the cells of these organisms flows to the higher concentration of salts without, literally bursting through the cell walls and killing off the microbes that are responsible for cycling the nutrients in the soil.
With the natural buffering action of soil bacteria and fungi lost or lowered, the soil’s pH is thrown out of whack; the soil pH gets lower and lower as more nitrate salts are applied.
All tiny particles in the soil, not just humus, carry electrical charges. These particles are called ions. Ions with a positive charge are called cations and ions with a negative charge are called anions. Positively charged particles are electrically attached to negatively charged particles. This is exactly what happens when opposite ends of magnets attract each other. When a positively charged cation attaches itself to a negatively charged anion, the cation is absorbed by the anion. Even microorganisms in the soil carry and are influenced by electrical charges.
Why does this matter? The surfaces of root hairs have their own electrical charges. When a root hair enters the soil it can exchange its own cations for those attached to clay or humus particles and then absorb the cation nutrient involved. Roots use as their exchange currency, giving up one hydrogen cation for every cation of nutrient absorbed. This keeps the balance of charges equal. This is how plants “eat”.
Most of us have a basic understanding of pH as a way of measuring acid or base substances. On a scale of 1 to 14, a pH of 1 is very acidic and a pH of 14 is very alkaline or base. The pH tells the concentration of hydrogen ions in the soil solution being measured. If you have relatively few hydrogen ions compared to the rest of what is in solution, the pH is low and the solution is acidic. Similarly, if you have a lot of hydrogen ions in the solution, then the pH will be high and the solution alkaline.
Plant roots feed by exchanging hydrogen cations for nutrient cations; this results in the concentration of hydrogen ions in the soil solution increasing. As this concentration goes up the soil’s pH goes up, or the soil becomes increasingly alkaline.
Things balance out in a working soil, however, because root surfaces also take up negatively charged anions, using hydroxyl anions as the medium of exchange. Adding hydroxyl ions to the soil solution lowers the pH of the soil
The pH created by nutrient-ion exchanges influences what types of microorganisms live in the soil. This can either encourage or discourage nitrification and other biological activities that effect plants. Fungi and bacteria have cations and anions on their surfaces, electrically holding or releasing the mineral nutrients that they take from the decomposition in the soil.Back