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Essential Nutrients for Plants: Part I
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Things are at a bit of a standstill currently as Mother Nature can’t seem to determine the thermostat setting, the wind seems to want to blow and much of the western half of Kansas waits for rain. Weather permitting, wheat ground is receiving nitrogen and herbicides. Some producers are hesitant to spend more money on their wheat crop with the price of wheat and dry conditions. Agronomically and economically, it is just as, if not more important under these conditions it to provide adequate weed control and make available necessary nutrients than under good conditions. At least those two sources of plant stress can be minimized. This week, and in several succeeding weeks, this column will discuss the essential nutrients involved in plant growth.
An essential nutrient (element) is defined as required for the plant to complete its life cycle. In other words, necessary for the plant to germinate, grow, flower, and produce viable seed. There are 17 elements required by all plants to complete their life cycle. They are divided into two groups – macronutrients and micronutrients. The difference between the two groups is the relative amount needed by the plant. Macronutrients are required in relatively larger amounts compare to micronutrients. That doesn’t mean they aren’t as critical to the plant, it simply needs small amounts of them. The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Micronutrients include iron, manganese, zinc, copper, nickel, boron, and molybdenum. The last essential element identified, nickel, was only determined fairly recently. While we know it is essential, we seldom see deficiencies and there really aren’t recommendation for it so this is the last time it will be mentioned. These elements are found naturally in the soil as the result of soil formation processes. Soils will vary in their native levels of these elements. Native levels are a function of the parent material the soil formed from and some may be brought in by atmospheric deposition, directly from the atmosphere, and as the result of deposition from flood waters.
Most of these nutrients are all taken into the plant as ions, they possess an electrical charge. Some are positive, termed cations, while others are negative, termed anions. One, nitrogen, is found as both an anion and a cation in the soil. The exceptions are carbon, hydrogen, and oxygen which are taken into the plant as water and carbon dioxide.
While a column is insufficient to provide great detail on the rules of nutrients and their management, one rule is critical to keep in mind – Liebig’s Law of the Minimum. The Law of the Minimum states: “the yield of a crop is limited by the deficiency of any one essential element even though all others are present in adequate amounts.” Often in agriculture, landscaping, or even as a homeowner, some nutrients are overapplied to compensate for poor growth and yield when the problem is really a deficiency of another nutrient. In plain English, the Law of the Minimum is stating that the weakest link determines the strength of the chain. If 16 of the 17 nutrients are adequate, the one that is deficient will limit growth and yield.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.