Supplementing Soil Potassium
Potassium (K) is often recognized as the nutrient with the greatest influence on many crop quality parameters. Nearly every crop, whether it is an annual, biennial, or perennial, goes through a rapid growth phase and an accompanying rapid nutrient uptake phase (Figure 1). Figure 1 shows growth and nutrient uptake for small grains but the curves are similar for many crops through the growing season. During the rapid phase of growth and nutrient uptake, many soils are unable to meet all of the nutrient requirements of the crop. It is generally known that 90 to 98 percent of the potassium in the soil is unavailable. Thus, increasing soil K fertilization often does not provide sufficient K to meet crop demands during this rapid nutrient uptake phase of growth.
Potassium has many different roles in plants. Among them are:
- Regulation of the opening and closing of stomata, and therefore, regulation of CO2 uptake
- Osmo-regulation - both uptake of water through plant roots and its loss through the stomata are affected by potassium
- Activation of enzymes – potassium has an important role in the activation of many growth related enzymes in plants, and it is essential for the production of ATP
- Protein and starch synthesis in plants - potassium is essential at almost every step of the protein synthesis. In starch synthesis, the enzyme responsible for the process is activated by potassium
When the supply of K is inadequate, these processes do not proceed at optimal levels necessary to achieve maximum yields. Studies have shown that supplementing soil K with foliar K applications during the rapid growth and uptake phase can help overcome the inability of the soil to provide adequate amounts of K. Ele-Max K-Leaf 0-0-30 is a good source of foliar K that is readily absorbed by the plant. It is very effective as a source of supplemental K during periods of peak demand, when the soil is unable to provide adequate amounts of K in order to achieve high yields of high quality crops.
- Curt Crossman, Product Manager, Pacific Area