Potassium Basics

potassiumPotassium (K) is an essential plant macronutrient taken up in large quantities, like nitrogen. In plants K does not become part of complex organic molecules. It moves as a free ion and performs many functions. Plants that are supplied with adequate K are better able to withstand stress, insect damage, and many plant diseases compared with plants low in K. Exchangeable K is measured by soil tests and is considered readily available for plants. Potassium can become “fixed” thereby not being available to the plant. Fixation and release of K by these minerals is dynamic throughout the year.

Right Source

The most commonly used K fertilizer source is potash. Compound fertilizers containing chloride, sulfur and/or magnesium are appropriate when soil supplies of these other nutrients are limiting. Liquid products or solid products can both provide adequate K to the soil.

Right Rate

Recommended rates of K application are based on both soil testing and crop removal. “Maintenance rates” are those equal to the quantities of K removed and are used to maintain soil fertility.

Right Time

Timing of P typically has little to no impact on crop use efficiency. Fall applications every year or every other year are common in our region.

Right Place

Potassium sources vary widely in their effect on the soil solution. Potassium fertilizer sources with a lower salt index may be used at higher rates when placed near or in direct contact with seed. Subsurface bands of K can provide benefits over broadcast applications when subsoil fertility is lower and when drier growing conditions exist.

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