Why do farmers need to test their soils?

American Society of Agronomy

The nutrients in the food we eat is a vital component to supporting a healthy lifestyle. But did you know that most of the nutrients in our food comes from the soil it is grown in? The October 22 Sustainable, Secure Food Blog explains why farmers need to regularly test soils to ensure optimum levels of nutrients.

Plants need 17 essential nutrients to function and carry their routine physiological processes. Of these nutrients, three are found in air and water: carbon, hydrogen and oxygen. The remaining 14 nutrients come from the soil. Since humans cannot see, touch or count nutrients through their naked eyes, they rely on scientific instruments found in soil testing laboratories to measure them.

This is a soil core before analysis. Farmers take these cores and other soil samples to be sent into labs for nutrient analysis. This allows them to use the optimum amount of fertilizer for the best yields.

That is why every fall, after the harvest of cash crop, farmers collect representative soil cores from 4 to 6 inches depth at several locations on their farm. They send them a soil testing laboratory for analysis.

Once a soil testing laboratory receives the soil, the lab dries, grinds and sieves the sample to make it uniform before running the tests. Then they perform the requested tests designed to quantify nutrients in the soil. The results provide information on the soil’s nutrient supplying capacity primarily phosphorus, potassium, and micronutrients.

Rishi Prasad, a scientist at Auburn University, explains that after soil scientists evaluate the soil test results, they can make recommendations on what is present in the soil and how much additional fertilizer would be needed to achieve optimal crop yields. Maintaining a record of soil test reports also provides valuable information on long-term changes in soil fertility. This allows farmers to make better decisions on fertility management to get optimum yields.