Manure is a great resource for crop production but it comes with limitations and issues. Variation in manure solids and nutrient levels is an issue from a crop-production standpoint. So researchers are studying how technology could be used to improve manure application and the nutrient-use efficiency of both nitrogen and phosphorus.
Near-infrared spectroscopy isn’t new technology. But it’s new to manure application, said Joe Sanford, an assistant professor in the University of Wisconsin-School of Agriculture at Platteville. He’s also a faculty researcher for the UW-Dairy Innovation Hub.
Near-infrared spectroscopy uses the near-infrared region of the electromagnetic spectrum. The system includes a light source and a sensor that detects the intensity of different wavelengths from a substrate. That can be correlated to various nutrients, Sanford said. In laboratory settings the technology has been used since the early 2000s to predict nitrogen and phosphorus in manure.
But until recently it hasn’t been tested in the field due to the effect of temperature variation and variation in solids concentration, he said.
“The ability to use (near-infrared spectroscopy) and apply manure in real time is appealing,” he said.
He and his team used John Deere’s HarvestLab 3000 in testing. It has manure-sensing constituent software to measure manure-nutrient levels in real time. It uses near-infrared spectroscopy and is installed on a manure tanker located near the applicator.
Manure didn’t come in contact with the sensor during testing. The box containing the instrument was placed on a pump line on the tanker. It had a piece of specialized glass; the light source was shot at the manure from the glass at an angle. It hit the manure through the glass and then what was reflected off the manure was recorded by the sensor, he said. That way none of the mechanical parts were in contact with the manure, just the glass. The glass did need to be cleaned and occasionally changed.
The system required specific hardware for installing the sensor in the manure line to allow it to measure the nutrients. As manure flowed from the tanker onto the field, the sensor took thousands of measurements per second, he said. In real time it predicted concentrations of nitrogen, phosphorus, ammonium and potassium.
“With the correct hardware, software and cab displays, farmers can see manure-nutrient content in real time during application,” he said. “They also can set specific nutrient targets and limits they’d like to meet during application. The system will adjust volume-application rates to meet those nutrient targets and limits.
“If we’ve uploaded maps to say exactly how much nitrogen or phosphorus we want (to apply), the system will then vary the application based on that actual concentration in real time.”
Such a system has the potential to reduce sampling variability from a manure lagoon.
“We know there’s a lot of variation as we’re pumping (from a lagoon),” he said. “We really don’t have a great solution for dealing with that. This has potential to really reduce that variation as we’re pumping from storage.”
After application the system could provide farmers a map showing the amounts of nitrogen, phosphorus and potassium applied to a field.
“When we return to supplement (the crop) with synthetic fertilizers, we would have a better idea of what actually went on the field with the manure,” Sanford said.
Near-infrared spectroscopy’s ability to “read” nutrients in real time also might have the potential to reduce a farmer’s regulatory burdens, he said. It could be generated in a spreadsheet that the farmer would send to a regulatory agency such as the Wisconsin Department of Natural Resources or the Wisconsin Department of Agriculture, Trade and Consumer Protection.
But there are in-field complexities, he said. The sensor has been shown to be more efficient at measuring nitrogen than at measuring phosphorus and potassium. More research is needed to improve the technology; several scientists are working on that. But a major issue is that there haven’t been many field studies to show how the technology could make an impact.
Sanford and his team conducted a test in fall 2022 when they applied manure at either 75 or 105 pounds of nitrogen per acre. For one treatment they used nutrient-sampling data averaged during lagoon pumping in 2021, he said. For the other treatment they used real-time sensor data. About 25 percent more nitrogen than needed was applied using the traditional method. The test was replicated five times; results showed the sensor technology consistently reduced variation as compared to the traditional method. The researchers evaluated field variability and how a system can potentially work in the field – comparing manure application based on using fixed-rate technology, variable-rate technology or a near-infrared-spectroscopy sensor.
Source: agupdate.com
Categories: Wisconsin, Crops