A farmer’s job is to feed the world, and in doing so he must test the resilience of our planet’s natural resources. To fulfill one of the many requirements for a certified organic farm, organic farmers must establish plans to not only use the soil, but to improve it for the future as well. Organic farming regulations require measurement and management of soil conditions, because balanced soil functions within ecosystem boundaries, habitat productivity, and the quality of human health.
One of the most basic factors that affects the availability of nutrients to plants is soil acidity, or pH. Simply put, soil pH is the measure of acidity or alkalinity. It’s measured in pH units, which goes from 0 to 14, with 7 as a neutral point. If soil pH isn’t measuring at the correct number, your crops won’t be able to process the nitrogen, potassium, and phosphorous they need to thrive. If you decrease the pH in your soil, you increase the solubility of zinc, copper, iron, and aluminum. You can increase the pH in your soil by applying lime, and thereby decreasing the solubility of these elements in your soil.
That’s all well and good, but how do you practically manage soil pH in your organic farm or backyard garden? The most accurate method of determining soil pH in the first place is by using a pH meter, which can be obtained from most farming and scientific supply companies. A simpler, but less accurate, method of pH testing involves using dyes that change color with increases or decreases in pH levels. Since pH can greatly vary from one area of a field or lawn to another, you will need to collect soil from several locations to combine into one sample for testing.
The ideal pH measurement for most crops is around 6, which is slightly acidic, or 7, which is neutral. As previously mentioned the most common corrective measure for farmers is to apply lime base on a soil test. In addition to lime, you can also use dolomite to raise soil pH. Alkaline soils can be harder to correct since farmers are often stuck using sulfur additives, which are expensive and only provide temporary correction. Organic farmers should read up on each of their crops’ pH requirements, since different crops do grow better at different pH levels.
Keep in mind that some mined materials, including gypsum and lime, can be contaminated with heavy metals that have restrictions under organic standards. If you’re serious about staying organic, you should always demand a certificate of analysis for these materials and confirm their authenticity before using on your crops. To read more about the importance of soil pH in organic farming, check out West Virginia University’s study on, “Maintaining Soil Fertility Under an Organic Management System,” and the Center for Environmental Farming Systems’ article, “Soil Fertility on Organic Farms.”