CONCORD, N.H. — There were a lot of eyes to the sky during a recent University of New Hampshire Extension workshop on aerial field scouting for crop production.
Gary Robertson, associate professor at North Carolina State University, has been working on field assessments of precision agricultural practices for three decades. His lab has a fleet of unmanned aerial vehicles, or UAVs.
Robertson said collecting and processing big amounts of data is necessary in order to use crop inputs efficiently and prevent problems before they get out of hand.
Scouting fields has been in practice since the dawn of agriculture, but newer technologies have enchanced scouting techniques.
“There are many platforms armed with a variety of sensors to monitor crops. Satellite, manned aircraft, UAV, ground vehicles and hand-held sensors are now giving us new pictures of our crops,” he said. “UAVs can give us resolution down to 1 inch, and their cost is a few thousand dollars and dropping. They can handle a payload of 5 pounds and fly for an hour. Roughly 45,000 farmers got UAVs for Christmas last year.”
An ultra-violet sensor can “see” problems caused by pests or pathogens long before they are evident to the human eye. Robertson studied a 25-acre cotton field using normalized vegetation difference spectra. The processed image showed healthy plants were green whereas diseased plants were yellow and red. To the human eye, the crops were green, he said.
Sensors can be used to identify different plant species and varieties. Some applications can be used to identify weed distribution, irrigation effectiveness, nutrient management and chemical applications.
UAVs can transport a pint to a quart of spray and can deliver it specifically to problem areas. UAV resolution is so good they can count the number of plants in a field and determine crop density.
Palmer amaranth, or pigweed, has been identified in fields using a UAV. In fact, the height of a weed relative to the crop has been measured with a UAV.
Manned aircraft using ground-penetrating radar have shielding to protect the pilot. UAVs provide a subsurface view of a field with little shielding.
Calibration strips, which vary the amount of nitrogen applied to a crop, are used to determine how much nitrogen should be applied to a field. Once calibrated, a sprayer using sensors can deliver the optimal amount of nitrogen.
Robertson said “there is a very good correlation between the data collected with ground sensors and that collected by UAV sensors.”
“Precision agriculture may not lower your fertilizer bill, but it will make you more efficient,” he said.
In addition to providing a farmer information to manage crops, Robertson said the same information can be used by farmers to prove they are in compliance with regulations.
Larger farms in the West and South, covering thousands of acres, use GPS-guided equipment and sensors for precision farming and to scout fields.
Consultants often guide farmers because they have the resources to deal with the amounts of data generated by remote sensing and other technologies.
Still, Robertson said the use of UAVs was feasible in fields as small as 20 to 30 acres.
Dorn Cox, executive director of Green Start, has been using aerial imagery to assess experiments on his farm. He said UAV technology can be used on fields as small as 2 or 3 acres.
The “data collected is great for record-keeping and planning,” he said.
Cox depends on open-source and patent-free technology in the construction of his fixed-wing UAVs and gets sub-inch accuracy using Wi-Fi.
Guy Steucek is a freelance writer who farms in Massachusetts and New Hampshire. He can be reached at firstname.lastname@example.org.