For hands-on testing with an emerging technology, the Farm Journal Test Plots installed a Valley Irrigation variable-rate system on an 80-acre field.
Farm Journal Test Plot evaluates irrigation technology
For more than a decade, the Farm Journal Test Plots has varied corn populations and nitrogen rates to respond to natural management zones in the field. In 2012, the crew added variable-rate irrigation to its site-specific farming portfolio.
In partnership with Valmont Industries, Inc., who provided the system, software and supporting in-field technologies, the Valley Variable Rate Irrigation (VRI) system was installed on a pivot owned by farmer Dan Meeker in Mason County, Ill., for a multi-year test plot. In addition to an upgraded control panel, valves were installed at each sprinkler head.
"This has been a customer-driven product," says Jake LaRue, director of research and development for Valley Irrigation. "Farmers are already using and realize the benefits of variable-rate planting, fertilizer application and spraying."
The chosen 80-acre field has two sandhills that have shown noticeable decreases in yield every year.
"Our goal was to increase the water enough on the sandhills to bring those areas up to the production levels of the rest of the field," explains Isaac Ferrie, who oversaw this Farm Journal Test Plot.
The pivot used in our testing was outfitted for Zone Control, which allows for prescriptions to vary by management zone in addition to sector. The crew divided the pivot into six control sections.
"Since this was our first full year with the technology, we wanted to understand how the soils respond to irrigation. For example, what impact would applying ½" of water have on soil moisture levels?" Ferrie explains. "For the first half of the growing season, we applied a uniform rate; then, starting in July, we used the VRI technology in two of the six control sections."
In the field, Irrometer soil moisture sensors were placed at three depths—6", 18" and 24"—in a representative zone for each of the four main soil types. These sensors are networked to a modem in the field that wirelessly transmits the data to the test plot crew.
A series of thermal images from Aerial Crop Reconnaissance Experts as well as NDVI maps provided by GeoVantage provided another way to monitor how the crop responded to irrigation.
"The thermal images show us crop temperature and the NDVI maps are a measure of crop biomass," Ferrie says. "We found that cooler crop temperatures and higher biomass levels correlated to higher yields."
Just enough water. The thermal images were used by Ferrie to make changes in the prescription maps from month to month. For this first year of collecting data, the frequency of the water was programmed on the farmer’s normal watering practices, and the test plot crew created the prescription rate maps.
- January 2013
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