By Gurbir Dhillon Ph.D.
Potassium is the third most critical element among the essential elements required by plants, after nitrogen and phosphorus. Potassium is required for photosynthesis, protein synthesis, nitrogen fixation in legumes, translocation of sugars, and starch formation. Thus, its proper availability helps with the production of better-quality grains and tubers in crops.
It also helps the plants adapt to stressful conditions, such as drought tolerance, and provides better resistance to certain diseases, insects, and pests. It helps strengthen plant stems and thus decreases susceptibility to lodging.
To perform these functions, plants generally take up large amounts of potassium, and its requirement is generally as high as nitrogen in the cereal crops. Its deficiency shows up as foliar symptoms in older leaves that began to turn yellow at the edges and die.
Fortunately, potassium is generally found in high quantities in most mineral soils. Canadian prairies soils are similarly rich in potassium. About three quarters of the cultivated land area has adequate potassium levels for crop production with the rest marginal to deficient levels.
Additionally, only about a fifth of the potassium taken by crops is exported in the grains, while majority of it is contained in the crop residue and returned to the soils. If, however, majority of the aboveground crop residue is removed, a large amount of potassium can be lost from soils due to its high requirement, as for example in case of a high-yielding leguminous forage crop. The next articles in this series, I will consider the different forms and availability of potassium in soils.
Read more about potassium in soils here