When we talk about input costs in farming, most of us immediately think of fertilizer, seed, fuel, or labor. But there’s one input that’s often overlooked—and yet it touches every acre, every plant, and every yield number: water.
Whether you’re running pivots, drip, or relying on rainfall, water is your number one fertilizer input. And the quality of that water? It might be helping your crop—or it might be tying up nutrients and holding your yields back.
Water Is the Messenger
Let’s think about this from the plant’s perspective.
That plant sends out its root hairs into the soil, and those roots absorb nutrients—not directly from the soil particles, but through the water surrounding them. The only nutrients that are truly available to the plant are the ones dissolved in the soil water. So if your irrigation water is out of balance or carries excess salts, sodium, or bicarbonates, it’s directly impacting the “nutrient soup” your crop is sipping from.
This is also what a rapid soil test is simulating. When labs run these tests, they’re mixing either your irrigation water or deionized water with your soil, placing it in a vacuum, and extracting the water—mimicking what the plant roots experience in real life. So if something’s off in that soil water, your plants feel it.
Here’s where it gets interesting: deionized water mimics rainfall. Rainwater is essentially deionized water—it might contain a few ions, maybe 25 ppm, but it’s clean and simple. That’s the environment your plants are in when you’ve had a rainy season and aren’t irrigating much. So when looking at your rapid soil test, pay attention to the deionized water result to understand what your crop is experiencing in a rain-fed year.
But the moment you flip on the irrigation system? Everything changes. Now, your crop is dealing with whatever is in your irrigation water—and you need to look at the rapid test results tied to that source. And if you’re using manure in your system, we’re going to learn even more in the years ahead about how manure affects those numbers. Sending in samples and understanding how manure inputs are tweaking your soil chemistry is going to be critical.
Water Can Work Against You
Take a field just three miles north of our shop. In 2020, it had nearly perfect rainfall—just the right timing and amounts. But when the pivot ran, the crop under it actually performed worse than the corners. That’s a red flag.
We dug in—literally. Soil tests revealed that calcium, although present in good amounts, was being tied up due to the irrigation water quality. What looked like a nutrient-rich soil on paper wasn’t delivering in the field because the water was interfering with nutrient availability.
Another grower in Nebraska saw a similar issue—burnt-up corn under the pivot. High sodium levels in the water were the culprit, throwing the soil balance way out of whack.
These situations aren’t rare. And they aren’t untreatable—but first, you have to know what you’re dealing with.
Rainfall Used to Help More Than It Does Now
Historically, rainfall acted like a mini reset button for soils. Back in 2000, the pH of rainfall was just under 4—acidic enough to help counterbalance some of the negative effects of irrigation water.
But that’s changed.
By 2020, the average pH of rainfall had risen to about 5.8. More recently, samples have shown a pH closer to 6.3. As we’ve cleaned up air pollution, we’ve also lost the acidifying effect that rainfall used to provide. So instead of getting a free “flush” with every rain, our soils are retaining more of the imbalances caused by irrigation water.
What Should You Do?
Start by testing your water. Just like you soil test, you need to know what’s in your irrigation water—sodium, bicarbonates, calcium, pH, and more. Once you understand the chemistry of your water, you can start making informed decisions about amendments, filtration, or other treatments.
And if you’re using manure in your system, start testing that too. We’re only beginning to understand how it affects soil chemistry—and those insights could help you adjust your fertigation strategy and protect your yields.
In a time when input costs are tight and every bushel counts, water quality could be the invisible factor affecting your bottom line.
Let’s stop treating water like a given and start treating it like the major input it really is.
Want help testing or treating your water? Reach out—we’re here to help.
