AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Fall 2002, No. 5

Potassium….

· encourages more efficient nitrogen use by plants,

· increases the photosynthetic production of carbohydrates which are necessary for energy production,

· stimulates storage of starch reserves in the roots of summer perennial grasses to provide greater protection against winterkill,

· enables plants to use soil moisture more efficiently,

· regulates the opening and closing of leaf pores (stomates) to allow proper air exchange for photosynthesis and for plant cooling

· improves root growth and enhances drought tolerance,

· decreases susceptibility to several plant diseases,

· stimulates increased nitrogen fixation by forage legumes and also increases plant protein content

· is involved in many beneficial enzymatic reactions.

· And it increases forage yields, grazing capacity, and potential farm profits.

Forage will take up potassium in the following amounts (pounds of K₂O per ton of forage dry matter): alfalfa=60; fescue, bromegrass, orchardgrass=50; bermudagrass, bahiagrass, dallisgrass=45; clover/grass mixtures=60. Grazing animals will return a large portion of the ingested potassium to the soil in feces and urine.

If your summer forage production seemed to drop off too rapidly as temperatures increased, if cool season forages do not respond to nitrogen rates as expected, check your soil test potassium levels. Remember, hay and silage harvests remove more potassium from the soil than any field crops. To sustain and improve production, the harvested potassium must be replaced.

Growers should consider grazing and hay demands, soil testing to evaluate their soil’s potassium-supplying power, and applying potassium fertilizer with other recommended nutrients this fall. Paying attention to potassium can improve forage and livestock production and increase farm profits.