Better manure management with new technology
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EmailUsing sensors to apply the right nutrients at the right time.
Manure is one of the most valuable resources on a farm. It provides key nutrients like nitrogen, phosphorus and potassium that crops need to grow. But manure isn’t always the same. Depending on how manure is stored and how well it's mixed before spreading, nutrients in it can change form, which can change how readily they’re available for the crop to use. That makes it hard to know exactly how many nutrients your crops are getting.
Usually, farmers take samples and send them to a lab to learn what's in the manure. But this takes time and costs money. And since nutrient content changes as you empty the pit, just a few samples might not tell the full story.
That’s why a group of researchers tried out a new tool: A manure sensor that works in real-time. This sensor uses near-infrared spectroscopy (NIRS) to read what’s in the manure as it's being applied. The goal is to help farmers apply the right amount of nutrients, especially nitrogen and avoid wasting manure or overapplying nutrients.
How the sensor works
The sensor tested in this study is called the John Deere HarvestLab 3000. Currently, the John Deere system is the only one on the market that has a real-time manure sensor. It was mounted on a manure tanker, along with a flow meter and a rate controller. As the manure was being spread, the sensor measured the nutrient levels instantly. Based on these readings, the system changed the tractor’s speed or the flow rate of the manure to apply the correct amount of nitrogen.
This system was tested in Wisconsin on silty soil. The team used three different nitrogen rate goals and compared the new sensor method with the traditional way of lab sampling and fixed-rate spreading. They also planted corn after spreading the manure to see if the crops responded differently.
What the results showed
In the first year of the study, the sensor did a better job of hitting the target nitrogen rates than the traditional method. The sensor’s applications were within 20-30 pounds of the target rate. The old method was off by a lot more, between 40 and 95 pounds extra per acre.
The sensor also measured phosphorus and ammonium during spreading, but lab tests showed that it wasn’t as accurate for those nutrients yet. Still, the ability to adjust nitrogen on the go is a big step forward.
Even though the manure rates were different, corn yield and nitrogen use efficiency were similar between both methods. That means the crops grew just as well either way, but the sensor did a better job of matching what the crop needed without overapplying. Avoiding over application of nitrogen can save the farm money through reducing input costs. It also saves on lost nutrients to runoff and tile lines.
One thing the researchers noticed was how the nutrient levels changed when the manure wasn't stirred or agitated as much. The sensor picked up big swings in nitrogen, phosphorus and potassium as the tank got emptied. This shows how helpful the sensor could be in making sure manure is spread evenly when it isn’t perfectly mixed.
What’s next?
The research team plans to keep testing the system over the next few years. They want to see if better manure spreading leads to better soil health and nutrient use over time. They're also updating the sensor's settings so it can more accurately measure phosphorus.
In the future, this kind of technology could help farmers get more value out of every load of manure. It could also help reduce runoff and protect water quality, since nutrients would be applied more precisely.
The goal is to give farmers and custom applicators a tool that saves time, cuts waste and helps crops grow better. It’s one more way that smart technology is making farming more efficient and more sustainable.
Manure is a powerful tool, but only if it’s used wisely. New sensing systems like this one could take a lot of the guesswork out of spreading. While there’s still more to learn, the early results are promising. With the right tools, farmers can make the most of their manure and grow strong, healthy crops.
This article is a synopsis of a presentation given by Joseph Sanford at the Waste to Worth Conference, April 7-10, 2025.
