Don’t Let Potassium Deficiency Contribute to Soybean Yield Loss!
It takes a smooth running engine (and many other important pieces of equipment) to provide maximum vehicle fuel efficiency – this conversion of fuel to power becomes “maximized” in terms of better mileage. A well-tuned vehicle can better navigate the various road conditions (steep inclines, starting/stopping, etc.).
When considering how your soybean crop is doing in terms of its “engine growth road performance,” you should consider scheduling periodic plant tissue tests, especially when soybeans are initiating blooms. Even though all the essential nutrients are important, I consider potassium (K+) as one of those critical elements keeping the soybean plant running smoothly during bloom, pod set and pod filling stages. Even though I’m featuring K in my comments, keep in mind N, P, S, B, Mn, Mg, Zn and other nutrients are equally important!
Soybean plants deficient in K tend to have weaker stems, may show some stunting, and result in a general slowing down of growth. Keep in mind that K has several important functions in plants including (a) photosynthesis and energy relations – K keeps the transfer of photosynthetic energy smoothly flowing into chemical energy, (b) enzyme activation – in soybeans K activates enzymes to help nodules make and move important food building blocks, (c) translocation of assimilates – K moves sugars and other food-building materials throughout the plant, and (d) water relations – K helps pull water into plant roots and reduce water stress.
Soybeans use large quantities of K especially during periods of rapid vegetative growth when root function and growth may be limited by dry, compacted or even wet soils (even though the soil analysis report shows adequate-to-high K levels). Keep in mind approximately 1.4 pounds of K2O is removed in every bushel of soybean grain and a ton of soybean straw contains over 19 pounds of K20!
If soybeans (and other crops) need additional K, Helena provides several superior foliar products such as Ele-Max K-Leaf 0-0-30. I’m reminded of a foliar trial conducted in 2018 in northeastern KS where K-Leaf was applied at 1 qt/A to soybeans at R1 (first blooms appearing). The soil test K was very high (584 ppm) on a well-drained silt loam soil. Those soybeans had an additional 5 bu/A advantage compared to the untreated check. This is an example of drier soil conditions limiting adequate soil K release and the foliar K application assisted in providing “available K.” Something to keep in mind. . .
- Sam N Bartee, CCA/CAC, Helena West Central Division AGRIntelligence Agronomist