Brought to You by the Letter K

ReachOut: Brought to you by the Letter K from Central Valley Ag on Vimeo.

Friends, last week I gave you a peek into the people and things that influence how I think about agronomy, sports, and life in general. Of course, that list wasn’t all-inclusive, and purposefully so—I’ll wait a few more years before I write my tell-all. One of the unmentioned though is the inspiration for today’s article. Almost five years ago now, this person got me thinking about potassium and its potential for changing the game of highly productive cropping systems, if only we could figure it out.

Potassium comes in a close third behind carbon and oxygen as the most critical of all the 16 essentail nutrients. It is vital to most of the reactions within a plant, from cell division to the formation of proteins and starches. The list of how it works to increase crop yields is longer than your Monday night shopping list. Potassium:

  • Increases root growth and improves drought resistance
  • Activates many enzyme systems
  • Aids in photosynthesis and food formation
  • Reduces respiration, preventing energy loss
  • Enhances translocation of sugars and starch
  • Produces grain rich in starch
  • Increases the protein content of plants
  • Builds cellulose and reduces lodging
  • Helps retard crop disease

That’s an impressive list, but I still know that at least one of you reading this is thinking, ‘But University recommendations tell me that my soil levels are high, so I don’t need to worry about applying additional Potassium.” To that I say yes, as they are written and correlated, you do not have to apply additional K. But. (There’s always a but.) Thanks to our friends at Winfield Solutions and the Nutrisolutions tissue sampling program, I can show you thousands of samples from our very own home state that show that we go deficient in Potassium very early in our crop’s life and then stay deficient all season long. The evidence is compelling enough to have changed my thinking about K in a major way.

Corn Tassel SS

This is where this nutrient gets all kind of complicated and fun at the same time. From the soils perspective alone, Potassium has quirks that no other nutrient has. It’s not highly mobile in most cases, not readily available in most cases, and requires a complicated intersection of two soil events that don’t always occur (and are short lived when they do) in order to become available. Potassium availability takes a soil that is nearing field capacity and is warmer than 70 degrees. Not extraordinary when you’re thinking about the soil surface, but what about at 2 inches deep? 18 inches? 24 inches? These events must co-occur in the active root zone, which makes their intersection quite extraordinary indeed.

The next twist adds another level of complexity. It’s not just about availability in the soil—it’s also about timing so that crops get it when they need it most. Check out Figure 1, courtesy of Dr. Fred Below and his staff at the University of Illinois. The good news about K is that once it’s actually in the plant, K is one of the most mobile nutrients as it isn’t bound up in the cell structure. A plant can reallocate potassium where it’s needed as the season progresses (which makes the distribution shown in the figure far less disturbing than it might look at first).

I wish that our inquiry into K had reached all its answers, but it hasn’t. What we can say is that we need to manage Potassium more like we manage Nitrogen (which would also make our utilization of N exponentially better). Otherwise, we have a whole lot more to learn about mastering K. Mastering it will take an understanding of timing, hybrid response, and probably a few tricks from the bag to help with the availability issue…Which I would love to talk to you more about, and will, in greater detail at the RD Summer Series events coming soon to an Answer Plot near you.