There are sensors that measure nitrate and phosphate in the soil today. They’re called ion-selective electrodes. But Matthias Young notes they tend to be expensive and imprecise — at least, not cheap enough or precise enough to help farmers make routine fertilizer rate decisions.

The University of Missouri researcher believes he is on to a better way to measure nitrate and phosphate. Recently, he published a scientific article proving his concept works, but it’s not yet ready for your field. In fact, it’s not yet ready for long-term greenhouse testing.

“Our sensor measures how quickly ions move through a membrane rather than how strongly they bind to it,” Young explains. He adds that current sensors rely on special molecules to bind with ions. These molecules run up the price tag on sensors.

In his lab-proven concept, he relies on a pulsed electrical current for measurements. He is confident that if his team can work out the kinks, these sensors will be more sensitive and cheaper to make.

“We envision hand-held sensors that farmers could use, and also sensors that could be left in the field,” Young says. “Part of the problem today is that existing sensors need to be recalibrated often. You just can’t leave them in the field.”

Unusual journey into ag research

If you’re guessing that Young is part of the ag school at the University of Missouri, you’re off base. He is an assistant professor of chemical engineering within the College of Engineering, with a joint appointment in chemistry in the College of Arts and Sciences. His research on this concept, spanning the past three years, was funded by a grant from the U.S. Geological Survey.

How did a chemistry professor end up chasing solutions for one of the hottest topics in agriculture? “I come from a small town, and my wife hails from a long-established farm near Cape Girardeau, Mo.,” he says. “My career just isn’t in agriculture.

“But when we started looking at problems, this one surfaced quickly. Friends told us fertilizer was becoming increasingly expensive, yet there was no good, inexpensive way to determine exactly how much to apply.

“We also discovered that when too much fertilizer is applied, it can run off and create environmental problems. We heard about algal blooms linked to excess fertilizer. So, it seemed like a problem worth tackling. That started our search for a cheaper, more practical way to measure key nutrients so farmers could better pinpoint how much to apply.”

What’s next for fertilizer sensors?

Funding from the initial grant is exhausted. However, Young is still tweaking his concept with the help of additional funding from a National Science Foundation grant. “What we’re doing now is learning how to fine-tune the polymer involved so it will hold up longer,” he says.

Right now, he is still testing the concept in the lab. Once issues with polymer stability are debugged, he can consider moving toward longer greenhouse experiments.

“We will need to come up with more funding to get this idea ready for extended field testing,” Young says. Nevertheless, he is confident they are on the right track, and that it will be possible to turn the concept into low-cost and long-life sensors in the future.