AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Winter 1998, No. 2
Potassium is no better or worse than any of the other nutrients in terms of being essential. Either an element is essential or it isn’t. There is no middle ground. The thing about potassium is not the fact that it is essential to the plant, but rather the fact that it is essential in so many ways.
Potassium does it all…or so it seems. It is certainly involved in a lot of essential processes in the plant. As a result, it is a major player in determining crop yield and quality. Consider the following functions and benefits of potassium.
Protein synthesis needs potassium. Without adequate potassium, nitrogen raw materials such as amino acids and nitrate accumulate in the plant. Regardless of how much nitrogen is applied, plants cannot convert that nitrogen into protein. This leads to low quality grain and forage.
Carbohydrate synthesis needs potassium. Photosynthesis is affected by potassium nutrition. So when potassium is low, photosynthesis is slowed. This means that the production of carbohydrates …the end-product of photosynthesis…is also slowed. This directly reduces the quality of many crops, including grapes, sugarbeets, potatoes, and stone fruits.
Carbohydrate transport needs potassium. Once produced, the carbohydrates must be transported to other parts of the plant for utilization or storage. This process requires energy that is provided in the form of ATP…adenosine triphosphate. Optimum production of ATP is dependent on adequate supplies of potassium.
Starch synthesis needs potassium. Carbohydrates are stored in the plant in the form of starch. Without adequate potassium soluble carbohydrates are not converted to starch. Perennial crops, such as alfalfa, are more subject to winter-kill without sufficient root reserves of starch.
Efficient water use requires potassium. Plants depend on potassium to regulate the opening and closing of stomates…the pores through which leaves exchange carbon dioxide, water vapor, and oxygen. When potassium is deficient, the stomates become sluggish, and closure may take hours rather than minutes. So the plants are more susceptible to water stress.
Potassium enhances crop quality. It improves physical quality, disease resistance, and shelf life of fruits and vegetables for our consumption and the feeding value of grains and forage crops for our animals. Fiber quality of cotton is also improved, including strength, length and uniformity. Quality factors are also enhanced in the field before harvesting. For example, potassium reduces lodging of grains and enhances winter hardiness of many crops.
And finally…potassium plays a role in activating many enzyme systems within the plant…at least 60 different enzymes that are involved in plant growth. This alone explains why so many different plant processes depend on potassium. Seemingly, if it occurs within the plant, then potassium is involved...directly or indirectly.
Potassium is just one of 17 essential elements. But let’s give it its due. Potassium does it all…or so it seems.