For good reason, there’s been increased discussion about 4R nutrient management. This easy-to-remember moniker refers to increasing fertilizer use efficiency by considering the right rate, time, placement, and form of a product (usually nitrogen and phosphorus).
The 4Rs are focused on fertilizer, but as Dr. Claudia Wagner-Riddle, researcher with the University of Guelph noted in her nitrogen presentation at January’s Ontario Agricultural Conference, there’s a fifth R that must enter all of these agronomic discussions: rotation.
It just so happens that that same week, Chad Anderson was my guest on The Agronomists, and he made the point that rotation is “the oldest and easiest way to increase yield.” (Check out that show here. There are more goodies.)
Every long-term rotation trial results in the same conclusion: the more diverse a crop rotation, the more yield in the system. What’s more, we also know that some is good but more is better. Adding just one crop to an alternation between two, i.e. corn and soy, reaps real benefits. Adding a fourth or more, especially if one of those is a fall-seeded or a perennial crop, further improves the overall resiliency of a system.
What does resiliency really mean, and why does rotation work? The short answer is, it’s complicated, but the larger answer is biology adapts, sometimes quickly. Nature also loves diversity — it’s really how it’s designed to work. Pest and predator, weeds finding niches, disease inoculum waxing and waning; as farmers it’s our job to understand the biology (good and bad) and work with it, not against it.
Resiliency comes from diversity — more and diverse soil microbe populations support healthy plant systems. Changing up crop type keeps weed species on edge and draws out the timeline to resistance. Nutrients and water at different rooting depths get found.
A diverse rotation is not perfect or the sole management tool, but it’s the most important.
Rotation, I argue, isn’t the fifth R at all — it’s the first.