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Developing Technologies to Better Measure Forage

By April Mueller, Research Assistant 1 - FTT,
Ryan Hicks, Electronics Technician
and Dillon Payne, Technical Program Manager, Ag Technology

Posted Aug. 12, 2019

In an effort to support the producers of the Great Plains, we have developed multisensor plant phenotyping platforms that indicate various parameters of forage. Measuring forages allows for more efficient and comprehensive analysis of real-time forage available to support beef cattle production.

Some of the sensors we use measure plant height to estimate yields, while others use multispectral wavelengths to infer characteristics of forage quality, such as crude protein content and digestibility. Using the data collected from different cultivars over several growing seasons, we are able to develop models that can predict both biomass and crude protein for various forages.

Our current ground-based phenotyping platforms are helpful tools for sampling forage, but these still require time and effort on our part. We aim to facilitate the development of increasingly comprehensive technologies to advance the automated process for forage estimation using remote sensing technology.

In looking to the future, we hope to be able to use satellite imagery to give producers land condition information in real-time. This leap forward will give producers incredible power in making educated economic decisions for their operation.

Developing Technology You Can Use to Measure Forage

The evolution of our ground-based phenotyping sensor systems begins with the Spider. The Spider is a high-clearance, narrow-wheeled tractor with sensors mounted on the front. It was developed for research to help our plant breeders make decisions on cultivar advancement and development for commercialization. Our plant breeders sow many various varieties/breeding lines in small plot trials to form a performance comparison between the varieties. The Spider employs high-precision GPS, allowing for easier trial mapping and visualization tools when the data is processed.

Soil Sensors

Because of the success of the Spider platform, we sought to develop a platform that could be used in grazing research but could also be applicable and feasible for a producer. With this goal in mind, we developed the “forage box,” which consists of laser, ultrasonic and an optical active sensor. About the size of a shoebox, this enclosed design is mounted on the front of a utility vehicle. Because it uses a GPS puck, the cost of this system is much more reasonable while still being able to effectively find forage averages across a pasture.

The forage box has been used to collect data on thousands of acres where cattle graze, and it has proven itself valuable in decision-making processes. Development is underway on a smaller, more user-friendly version of the forage box that we hope will be commercially available for producers in the future.

Measuring Forage Biomass and Quality

Measuring plant height is the first step to predicting forage biomass. Historically, plant height has been measured using a grazing stick and, in recent years, with a rising plate meter. While these methods are effective, they are both labor and time intensive. In an effort to calculate plant height more efficiently, we use two different sensor types. First, our systems contain an ultrasonic sensor that sends sound waves toward the plant canopy and measures the length of time it takes for the waves to return. This sensor is similar to a depth finder used on fishing boats. Second, we use laser rangefinder sensors, which trigger the laser to return to the sensor when an object breaks the laser’s field of view. These two different measurements give us a depiction of what a plant stand looks like — whether it be short, tall, thick or sparse.

Another fundamental aspect of forage estimation includes measurement of forage quality. For this assessment, we employ multispectral sensors. This technology sends out three different wavelengths of light that are beyond the scope of human sight and measures the reflected wavelengths to estimate a plant’s degree of greenness — or lack thereof. The sensor uses the data returned to measure plant health. In order to tie all the data together and down to an accurate location on a map, we tag the data with a location using GPS. Our high-precision GPS systems, useful in small-plot research trials, utilize a Novatel radio with OmniStar correction, which provides greater than 15 centimeters of accuracy. Projects that utilize the forage box, such as those on grazing and rangeland areas, require less accuracy, and a GPS puck will suffice. The puck makes the forage box a much more cost-effective platform than the Spider.

Another implement currently used to calculate forage biomass is a forage tower. The towers house a scanning laser, similar to those used in self-driving cars, that detects an object’s distance from the sensor. They will be deployed on cattle pastures to record and transmit forage biomass data to a home computer. Because the units are radio-enabled, they require minimal human mediation for data collection events. Also, these towers allow data collection multiple times each day. This relayed information, when coupled with the Tru-Test Walk-Over Weigh systems, gives comprehensive information on forage quality in the context of animal performance.

Future Challenges and Opportunities

While we operate these systems year-round to measure various agricultural systems, we are pressing forward to employ more efficient systems that require less human intervention to operate. Every new technology requires “ground-truth” validation to ensure the measurement events are giving us data that correlates to the forage that is actually on the ground. With this challenge at the forefront, we are now working to deploy these sensor technologies on a UAV platform, providing both increased efficiency and greater producer availability to this technology.

The UAV-mounted Raptor ACS-225LR-IRT Aerial Crop Sensor contains similar sensors to the Spider platform for plant measurements, a high-precision GPS system, and a mode of transportation with greater flexibility to conditions on the ground. While the Spider system is a high-clearance option, there are still varieties that grow too tall for effective measurement with this equipment. The freedom of an UAV eliminates this limitation. Also, driving the Spider across forage after a rain creates the potential for getting stuck in the mud and tearing up the existing plant stand. While UAVs have their own limitations, they provide solutions to current technology with greater efficiency and opportunity in high-throughput phenotyping systems.

One challenge we face is the expansion beyond monoculture agricultural systems. Most producers have some amount of land that exists as native rangeland, polyculture or multicrop systems. It is important to note these sensor systems are sampling tools and are effectively building average measurements of an area. With these averages in plant height and health values, we can build statistical models that predict forage biomass and crude protein. In a mixed forage system, building models becomes increasingly complex as the included species increase. Deploying sensor systems on polyculture forage requires a comprehensive system of sensors and models built for forage combinations similar to the forage at-hand.

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