By John Fulton
Liquid manure serves as a viable source of fertilizer in crop production. However, the potential variability in nutrient levels of liquid manure during field application can pose a management challenge. Currently, manure is applied to a field at a constant rate without feedback on whether nutrient concentration and dry matter (DM) vary when a lagoon is pumped. Today, sensor technology has been developed to measure nutrient concentration and dry matter (DM) of liquid manure.
Liquid manure sensors rely on near infrared (NIR) spectroscopy, which creates a reflectance in the near infrared range of light, which in turn measures and uses it to estimate the amount of individual nutrients and dry matter (DM). Individual nutrients in liquid manure respond differently to the NIR spectrum of light and reflect that light differently. This allows the sensor to capture a cross section of the manure flow and quantify each nutrient based on the energy reflected. Combined with ground velocity and manure flow (gallons per minute) estimated using a flow meter, this data produces a real-time estimate of pounds applied per acre per second (1 Hz). Currently, these sensors measure the following variables in liquid manure: total nitrogen (N), ammonia (NH4), phosphorus (P), potassium (K), and dry matter (DM).
Companies currently offering liquid manure sensor technology include John Deere (Harvest Lab 3000), CNHi (NIRXACT), and Zunhammer (VAN Control Dual Measuring System). Each of these technologies can provide real-time feedback to an operator during lagoon pumping and field application, and allows application maps to be created that spatially reflect the nutrient levels and dry matter content applied to a field.
The benefits of manure sensors include real-time feedback of nitrogen and phosphorus levels during field application, mapping capabilities to visualize nutrient levels in fields, electronic recording, and an additional layer of analysis with yield and other field maps to better plan for the next season. These sensors can greatly improve manure application while providing data for the next nutrient application. Additional technologies that can be added include automatic ground adjustment and variable rate application. Automatic speed control adjusts the tractor’s ground speed to maintain the target nitrogen or phosphorus concentration or rate during field application if the nitrogen or phosphorus concentration changes during application. Contact a dealer to learn more about this sensor technology that can improve manure application in fields.
For more information on precision agriculture technologies, visit or follow OSU’s precision agriculture research on X and Facebook at @OhioStatePA.
Dr. John Fulton is a professor in the Department of Food, Agricultural and Biological Engineering at Ohio State University and can be reached at [email protected].
