Individually, N, K, and S each play a significant role in a plant’s life cycle.
N works mainly at the cellular level as it comprises a big portion of DNA and ATP (which, for those of you digging deep into your last biology class, is essentially a plant’s battery).
K functions in many regulatory processes like ionic balance, which dictates turgor in plant cells and allows for the ease (or not) of water and nutrients to enter a plant, and stomatic control, which controls water usage. K also assists in regulating disease resistance and drought tolerance, activates at least sixty enzymes critical to plant growth, and is crucial to plant development and reproduction.
S is a significant component in many amino acids. It is necessary for chlorophyll formation and in legumes, is necessary too for nodule formation.
To achieve peak growth and production, your crops need not only enough of these three all-important nutrients, but they need them also in the correct ratio and available at the right time and therein lies much of the challenge of nutrient management.
Imagine that you are tasked with assembling cars. You’re in a giant warehouse whose shelves are filled with different car parts: pistons, spark plugs, gas tanks, brake lines, and on and on. So you build a car, pulling every necessary part from the shelves. And you build another and another and so forth until one time, you walk to a shelf and find that there are no more tires. Which means that your car building is over, my friend. At least until someone gets you some more tires.
This is exactly what your plants do with N, K, and S, except that instead of building cars, they use the nutrients to build sugars and proteins. N, K, and S, though they all play vital individual roles, come together in the important processes of protein synthesis and photosynthesis. As your plants accomplish these processes, should they ever reach onto the shelves for some necessary component and find it missing, that process, like your car building, comes to a sudden halt.
Which is why having enough available nutrients in your soil is so critical. Of the three that we are hitting on here, each has its own challenges and quirks when it comes to being sufficiently available:
N, as you well know, is highly mobile in the soil. In its ammonium form, it is relatively stable, but what form soil N is in is highly dependent on weather and soil conditions—two things over which we have little control.
K is far less mobile, which makes it less available. It spends much of its time in the soil trapped in the colloids of clay molecules and requires water and heat to escape. Understanding this soil interaction dynamic is tricky and important to your nutrient management.
S acts much like N in the soil. The main issue with S is that there is rarely enough. If you imagine your plants reaching for the shelves to build sugars and proteins, S is often the first component they find in low supply and exhaust in short order.
In addition to the different levels of mobility and availability each nutrient has in the soil, other complexities abound. The ideal ratio of N to K to S changes by plant species, and may even change by hybrid. The mechanics of nutrient uptake from soil to plant are not the same nutrient to nutrient. The timing of peak demand varies nutrient to nutrient as well, which means that the ideal ratio of N-K-S changes over time.
If the management of these nutrients is starting to sound like a game you can’t win, I sympathize. The wide world of science always seems to pose questions much more readily than it does answers, but don’t lose faith. Though they can be challenging to come by, answers do exist. Growers and researchers together have developed practices and ideas to guide proper nutrient management and our understanding of the best approaches to ideal management is ever sharpening. Sharing these practices and approaches with you is a major goal of our RD Summer Series upcoming on May 29th, June 3rd, and June 5th. I hope that you’ll join us at the Answer Plot, where the rubber will meet the road and the science will meet the soil with the goal of supporting peak growth and production of your crops through 21st century advances.