Finally, friends. My track record with series articles is dismal, so this is likely a few weeks late for maximum impact, but here it is regardless. Ta da! Meet the two nutrients I have been hinting at for weeks: potassium and sulfur.
No one wins the breakfast pizza, though I do owe one intrepid reader a coffee for good effort.
So we talk about nitrogen all the time—it is the Kardashian of nutrients. Which is partially deserved: we put it down in the biggest quantities and its cost and impact in our fields are unmatched by other nutrients. But. Kim just isn’t Kim without Kanye, right? Or without Kris. She needs these others to be the biggest and best Kim she can be. So it is with nitrogen and potassium and sulfur.
Potassium is a macronutrient that you all know and love. It acts a bit unpredictably in the soil, but it is critical to nitrogen use in our plants as it affects a plant’s ability to uptake and allocate nitrogen to best effect.
The rapid uptake of nitrate into a plant is dependent on the presence of potassium in the soil solution. Without sufficient K, a plant’s ability to take in nitrates is hobbled. Once inside the plant, potassium is further necessary for reduction, the process by which nitrate is changed to ammonium. As if these two functions don’t solidify the necessity of K, potassium also regulates the glutamate/glutamine cycle in corn plants, which drives the reallocation of N throughout the plant. Without proper reallocation, a plant may show signs of nitrogen deficiency in important places like leaves and grain, but an oversupply of N in the stalk.
A lack of potassium in the soil negatively affects a plant’s efficiency using N in many ways then. Even given an abundance of N in the soil, a lack of K can cause, essentially, a nitrogen deficiency in plants as plants are unable to take N in and/or unable to allocate it properly.
Sulfur is a macronutrient-to-be (the topic of a previous article, if you’re curious). With decreasing amounts of sulfur present in the atmosphere due to decreases in certain types of air pollution, we can’t count on our plants sourcing sulfur from the elements in sufficient quantities. So, we must apply, to the tune of one pound of sulfur for every five pounds of nitrogen. And we must apply because sulfur, like potassium, enables the use of nitrogen within our plants. Sulfur is critical in ATP transfer, a process that drives nitrogen up the plant to prevent deficiencies in the important further reaches of the plant: again, the leaves and grain.
So, yes—we talk about nitrogen all the time. But when we talk about the efficient use of nitrogen, the conversation is woefully incomplete without a discussion of potassium and sulfur too as both enable our plants to take in more N and use it efficiently and effectively.