Soil testing can yield important information for growers and grazers about the general health, fertility, structure, and physical properties of any given land and its suitability for different crops. By combining diligent record keeping with professional soil testing, it is possible for modern farmers to build up knowledge about the characteristics of their farm and individual fields. By taking action before problems develop, it is possible for you to make accurate predictions to better plan fertilization, inter-cropping, and crop rotation strategies months or years into the future.
Midwest Laboratories offers four different soil testing packages, including a basic soil test, advanced soil test, complete soil test, and soil testing for homes and gardens. These packages include individual tests for the presence of quick and slow release phosphorous (P1 Weak Bray and P2 Strong Bray respectively); soil pH, which is a measure of relative acidity; levels of the available cations found in fertilizers which are essential for plant health (Exchangeable potassium, magnesium, calcium, hydrogen, and nitrates); soil nutrient retention potential (Cation Exchange Capacity); and levels of important trace elements such as copper, boron, iron, manganese, and zinc. Other tests include measures of organic matter and microbial activity, a Buffer Index report, and a measure of excess sodium and lime content.
One of the most important tests we perform is the soil pH test. pH is a measure of relative acidity running from 1 to 14, with 7 being considered neutral, lower numbers acidic, and higher numbers being alkaline. Microbial activity can occur in both acidic and alkaline soils, however, the best balance of desirable microbes is achieved in soil that is relatively neutral at around pH 7.
In chemical terms, soil with a low pH has an abundance of hydrogen (H+) ions, which carry a positive charge (cations). In acidic soils, sulfur, nitrogen, calcium, magnesium, and potassium, and phosphorous become unavailable in forms that plants can use. Soil with a pH of above 7 is alkaline, with an abundance of hydroxyl (OH-) ions. Alkaline soils tend to be deficient in important trace elements which plants need to remain healthy. Soil that is very acidic or alkaline can eventually be toxic to crops, and can cause the soil to change in such a way as to hinder crops in future years. Accordingly, we advise that you pay close attention to the pH levels of your farmland, and take preventative action before a problem develops, or appropriate corrective measures where needed.
A Cation Exchange Capacity test is a measure of the soil’s ability to retain nutrients as cations available for plant use over time. The levels of clay and other soil components will change this value. A higher value is desirable, indicating that soil nutrients will not simply be washed away during irrigation, but rather, will adsorb to clay and humus particles within the dirt. Fields determined to have a lower CEP are still useful, but may need to be monitored more closely to maintain optimal usefulness.
With proper care, it is possible to improve the overall health of a field over time by employing good farming practices such as planting alternating strips of crops, known as inter-cropping, and letting fields rest while growing nitrogen-fixing crops like legumes (peas and beans), referred to as crop rotation. Periodic soil testing will allow you to assess when the best time to take action is, and more importantly, how effective your existing regime has been.
Despite its ancient roots, agriculture has remained one of the most active scenes for new advances in science for thousands of years. Modern farmers are among the first to embrace new technologies when they first become available, and as our understanding of what soil testing and its results imply improves, so too can your response in dealing with nutrient deficiencies and chemical imbalances. Each field has a different history and characteristics, so with the health and fertility of any particular field changing across its breadth, seasonally, and over the course of years, care must be taken when collecting samples.