Getting the Dirt on Dirt! – Understanding your Soil Test Results.

Mark Williams  |  7/28/2015 7:12:43 PM


To be fair to the agronomist, dirt is soil that’s out of place. Whether it’s in your garden, lawn or field routine soil sampling can be beneficial. The routine soil test report contains a multitude of information. Making sense of this information is not always as simple as reading the numbers listed for each element. Soil tests indicate the relative capacity of soil to provide nutrients to plants.

The most important information to be utilized is the soil pH. Soil pH is an indication of the alkalinity or acidity of the soil. Soil pH of 7 is neutral and most plants prefer a soil pH range between 6.0 and 6.5. The availability of most soil nutrients is greatest at or near the soil pH of 6.5. When the soil pH raises above this level the trace elements such as iron, manganese, copper, and zinc become less available. Soil test recommendations will indicate if amendment with lime of sulfur is required to change to the soil pH

Nitrogen (N) is a component of protein and enzymes found in chlorophyll, nucleic acids, and amino acids, which control almost all biological processes. Phosphorus (P) is important for plant development including the development of the root system, normal seed development and uniform crop maturation. Phosphorus (P) is essential component in photosynthesis, respiration and cell division. Potassium (K) is responsible for regulation of water usage in plants, disease resistance, and stem strength. The soil test results will give a recommendation of how much N, P and K to apply to achieve plant productivity.

Secondary macronutrients consist of calcium (Ca), magnesium (Mg), and sulfur (S) which are required for specific plant functions. Calcium is essential for cell elongation and division. It is specifically required for root and leaf development, plant function and cell membranes, and formation of cell wall compounds. Magnesium is a primary component of chlorophyll and is therefore actively involved in photosynthesis. It is a structural component of ribosomes, which are required for protein synthesis and is involved in phosphate metabolism, respiration, and the activation of several enzyme systems. Sulfur is required for the synthesis of the sulfur-containing amino acids, which are essential for protein formation. Sulfur is also involved with the development of enzymes and vitamins as well as the promotion of nodulation for nitrogen fixation by legumes. The micronutrients essential to plant growth include boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), and chloride (Cl), which are needed only in trace amounts by the plant.

The fertilizer recommendation will indicate the amount of N, P, & K required for the specified crop for the entire growing season. It’s usually best to divide the total amount of fertilizer to into two or three applications depending which crop you are growing.

For more information on this topic contact Mark at 225-389-3056 or visit our website at

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