I’m going to come over to your house. I’m going to come over and eat five pieces of Halloween candy. But don’t worry: I’ll come back tomorrow and replace three.
Imagine if I kept doing this—eating five and replacing three. It’s pretty clear, right? You’re getting the short end of the stick. I might be replacing some of what I deplete, but you’re still minus two pieces of candy at the end of the day. At some point in the future, you’ll just flat out run out of candy.
This, friends, is what is happening to our soil. We’re eating all its candy, or, er, its nutrients.
From 2005 to 2010, the INPNI conducted long term research on soil samples from across the Corn Belt. The results are alarming. We’ve mined our phosphorous levels by nearly 50% and potassium, zinc, and sulfur all are reaching near critical levels for the sustainment of high yield production. In other words, we’re removing nutrients from the soil at a higher rate than we’re replacing them. The consequence of this is something called the “nutrient cliff.”
As we approach this cliff, our yields will continue to get larger and larger, but once we hit the cliff? We’ll see a sharp and dramatic decrease in our yields. (Much like falling off a cliff—get it?)
When might this happen? I don’t really want to find out.
We’re barreling toward a time when our soil will no longer sustain high yields. What the cost of fixing such a situation might be is completely unforeseeable, but certainly, it won’t be cheap. What is foreseeable though is the action needed to avoid this cliff and the cost of such avoidance. We don’t need to be barreling headlong over it—we need simply to replace the nutrients that our crops remove, and, for good measure, build a little, which will not only help us avoid the cliff but turn us away from it.
I’m certain that no grower in existence is skimping on nutrients in an effort to accelerate us toward the cliff, but there are many growers in existence skimping on nutrients in an effort to save money in a tough economic situation. Perhaps we think that our soil won’t truly miss the nutrients, or perhaps we intend to replace them later, when the markets are kinder and the cost of inputs lower. It’s a fine thought, but an incorrect one as nutrient depleted soil will yield less than soil replete with nutrients (thus costing you money). Furthermore, even if input prices do drop, your cost will yet be high since you’ll have that much more to replace. A 50% drop in corn prices only equates to a 12% drop in the optimal application rate of nitrogen—even economics doesn’t support coming up short when it comes to nutrient replacement.
The nutrient cliff is not a probability but a definite outcome, much like your running out of candy would be a definite outcome according to my unbalanced removal/replacement plan. We need to set the goal today of reaching target levels of nutrients in the soil and replacing them completely enough to maintain those target levels. Every move we make—to skimp on nutrients in an effort to save money, to replace nutrients completely with an eye toward the future, to write our soil an IOU—every move delays our arrival to the cliff or jumps us toward it. So move carefully. If you’re considering trimming your fertility plan due to low corn prices, don’t! There’s a cliff ahead.