Achieving this goal involves gathering plant and soil water status information through GPS, a lightbar system, drone copter, sensors, and other tools.

Collected information is sent to one or more computers through data acquisition systems for data tabulation. The information would help producers precisely determine when and how much to irrigate.

UC Davis Extension Specialist Bruce Lampinen assists the research team in canopy tests to determine whether a lightbar mounted on a retrofitted Kawasaki Mule four wheeler travelling across the orchard floor can effectively and efficiently measure photosynthetically active radiation or PAR – the sunlight absorbed by the leaf.

Absorbed light energy, through a process called carbon dioxide assimilation, produces a crop.

Lampinen had demonstrated that this information can help predict potential yield and assist in managing crop canopy. Upadhyaya and his students are exploring the use of PAR absorption data in irrigation and potentially in nutrient management.

The other question is whether a drone copter outfitted with multispectral and thermal cameras can more accurately and efficiently gather the data.

The jury is still out on the answer.


Want access to the very latest in agriculture news each day? Sign up for the Western Farm Press Daily e-mail newsletter.


Inside Bainer Hall at UC Davis, associate development engineer Jedediah Roach overseas the data collection and analysis performed by the drone copter. With a video game-type controller, Roach operates the experimental craft in the Nickel’s field tests.

“With the lightbar and the copter, we are able to look at trees from below and above,” said Roach. “We will proceed with whichever method is more efficient and cost effective in the end for the producer.”

Whichever system works best, it could help the producer make more accurate irrigation decisions to save water and nutrients while improving agriculture’s environmental footprint.

Another part of the study involves the use electronic sensors and controllers attached to a solar-powered wireless network mounted on posts in the orchard which can monitor soil and plant water status. The node can also operate latching solenoid irrigation valves.

The third-generation sensor suite, which can monitor plant water status by observing canopy temperature, wind speed, relative humidity, and PAR, is under development to recommend when and how much to irrigate.

Preliminary tests suggest that one node per one-third acre (50 trees) could be economically feasible with a yield increase of about 15 percent. One node per acre (150 trees) could be feasible with a 5 percent yield increase at the costs of current advanced technologies.

Information is fed into a computer, such as the universal navigation computer developed by Trimble. Trimble’s system includes a touch-based 12.1-inch-color monitor inside rugged housing, along with an improved GPS for use in heavy canopies, an interface to configure data logging, and a method to extract the GPS-tagged data.

From there, a visualization and decision support system would process the data into meaningful 2-D or 3-D maps. A variable rate water application system, including a network of UC Davis-built sensors and controllers, would include variable rate irrigation strategies for the grower to consider.