Utilizing sensor technology to increase wheat yields and protein content in irrigated agriculture is the cornerstone of research conducted this year by the University of Arizona.
The UA project uses sensors to locate low and high yield and protein content areas across fields, determines the reasons for the differences, and allows farmers to better utilize production inputs including water, fertilizer, seeding rates, and weed control for optimization.
The one-year research project is funded by the Arizona Grain Research and Promotion Council.
“We need to better understand how soil and plant properties impact wheat yield and protein content at the field level,” said research project leader Pedro Andrade, UA precision agriculture specialist. “This information is the key to formulate management practices to optimize yield and grain quality.”
Andrade is based at the UA’s Maricopa Agricultural Center, Maricopa, Ariz.
“Wheat growers receive a higher income for increased yield and protein content,” Andrade said. “We want to put more money in their pockets.”
Fine-tuned input management is more common in the largest U.S. wheat-producing areas including the Great Plains and the Midwest.
Current efforts by the UA are addressing technology development better suited for the semi-arid farming systems in Arizona. Andrade says managing inputs in Western irrigated agriculture is very challenging. High sodium levels in the water, for example, can change how inputs impact crop yield and quality.
This year Andrade conducted a field-scale study on soil and plant variables on 37 acres (two fields) of common Durum wheat managed by grower Karl Button of the Button and Bohnee Farming Partnership. The 3,500-acre wheat, cotton, barley, alfalfa, and Bermudagrass operation is located on the Gila River Indian Reservation in Sacaton, Ariz.
Andrade and John Heun, UA research specialist, installed two types of “on-the-go” sensors on a rig designed to measure the electrical response of soil and plant canopy health across the field.
In January, a small tractor pulled the rig through 6-inch tall wheat at the 3-4 leaf stage (by the end of the tillering stage and before jointing). The rig was pulled through early enough in the growth cycle to prevent permanent plant bruising and damage from the equipment.
The Veris 3000 sensor on the rig emitted an electrical current into the soil to measure electrical conductivity (EC) to characterize the soil’s water-holding capacity at 1 and 3-foot depths. The soil types in the fields ranged from sandy to clay loam.
“We wanted to determine if the Veris sensor through EC could help identify whether variable-seeding and fertility rates, along with changes in the irrigation schedule in different soil types, could increase yield and protein content,” Andrade said. “Preliminary results of this project suggest that high EC areas are associated with lower protein content.”
Holland Scientific’s Crop Circle ACS-470 optical sensors mounted on the rig distributed modulated polychromatic light to the plant canopy. The sensors recorded the amount of light reflected by the leaves in the visible and near-infra-red regions of the electromagnetic spectrum.
The amount of reflected light can pinpoint the size, vigor, and condition of most crops, Andrade says. Healthier and larger plants absorb more light. Generally speaking, more reflected light signals smaller plants and plants with inadequate nutrition.
The output signals from the EC and optical sensors were geo referenced with input from a GPS (global positioning system) receiver. By the end of the season the information was analyzed in the spatial context using geographic information system (GIS) software.
Andrade, Heun and Button harvested the wheat in early June, a few weeks later than usual due to cool and wet spring weather conditions.
The combine was outfitted with a Campbell Scientific CR3000 micrologger, a Trimble 332 AgGPS system, an Ag Leader yield monitor, Trimble navigation light-bar, and auxiliary equipment to record yield and protein levels across the study fields.
Andrade collected three wheat samples per acre. The samples were analyzed in a laboratory to determine precise protein levels. The original sensor readings were compared to the GPS-generated maps. The maps clearly showed actual production conditions across the fields.
The findings were then compared to Button’s production management practices throughout the season.
“We currently measure our protein percentage during harvest by the traditional method,” Button noted. “Grain is taken from the field by the truckload to the elevator where yield and protein information are measured by the overall truckload. This method prohibits me from knowing exactly where yield and protein levels differ in the field and where I can better manage the inputs.”
Button added, “This UA research allows me to pinpoint yield and quality levels in the field, determine the reasons why they occur, and then adjust my management tools as needed for maximum yield and quality.”
Andrade’s initial analysis suggests that EC soil variables have a strong link to protein content. He hopes to continue the research next year including the investigation of other potential factors.
“I am confident that there are ways to implement site-specific management of production factors in irrigated wheat to optimize the protein content through variable rates of nutrients and water,” Andrade said.
The sensor canopy reflection test failed to demonstrate a strong tie to yield and protein this year. What is likely needed, Andrade says, is to extend the period of plant monitoring beyond the early stages of development and explore the potential application of remote sensing closer to the application of fertilizer supplements.
Button has farmed this ground for 30 years. Soil management is crucial and challenging due to various soils and the water supply. Clay loam soils are located on farm ground close to the usually dry, nearby Gila River. Most of the farm’s water for irrigation is drawn from wells which contain higher sodium levels which reduces crop yield and quality.
Button applies about 200 pounds of sulfur per acre at pre-plant to combat the sodium. Sodium reduces the plant’s ability to uptake water.
“The sulfur application helps, but it’s expensive and takes about five years to make a real difference,” Button said. “Sulfur is not an overnight answer.” Soil bacteria consume sulfur creating sulfuric acid which helps neutralize the sodium.
Button is excited by the initial field trial results which offer him better, more cost-effective ways to increase wheat production and quality.
Nitrogen (N) is the critical ingredient in wheat protein development. Button has learned to apply more N in sandy soil and less N in clay loam soil.
“Sandy soils also don’t retain water as well,” Button said. “Clay soil with a lot of sodium grabs the water and the plants can’t get it. The sodium is the culprit.”
Andrade will seek funding to continue the research next year. While wheat seed is currently planted uniformly in fields, Andrade is analyzing alternatives, including to rig a grain drill to provide GPS-based variable seed placement to potentially boost yields.
“In the world of high technology we make extensive use of auto-guided tractors for some operations,” Andrade said. “We are exploring the benefits of using the enhanced capabilities of these tractors in close cultivation, variable rate planting, and nutrient management.”
Varying the amount of seed in the ground is an idea worth pursuing, Andrade says.
The EC data and software can instruct the controller where to apply less and more seed to maximize yield and quality while controlling costs.
The University of Arizona’s Mike Ottman provided plant physiology assistance in the research project.
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