Davis, Calif.—Researchers at the University of California, Davis, and other schools in the western states are more than halfway through a project to create and evaluate a system of inter-connected sensors that could be used to help monitor and control irrigation for winegrapes and other crops.

The three-year study of precision canopy and water management is being funded through a $2.5 million grant by the U.S. Department of Agriculture. Staff at UC Davis are working with researchers at Washington State University, the University of Arizona, New Mexico State University and Oregon State University on the project.

The study is primarily focused on almonds and walnuts, but researchers are also exploring applications in the vineyard. The ultimate goal is to develop a system of sensors to help inform farmers about their plants’ water needs as well as create models and detailed computer-generated maps for crop and irrigation plans.

The project is evaluating several different types of sensors including a LIDAR and lightbar system installed on a Kawasaki Mule utility vehicle and a drone helicopter equipped with a multispectral camera. Researchers are wrapping up the second year of the project.

Dialing in deficit irrigation
Dr. Mark Matthews, a professor with the UC Davis Department of Viticulture, is a plant biologist who has studied deficit irrigation on winegrape vines for years. His work is now being used as part of the study about precision canopy and water management.

He said this past summer he enjoyed watching the engineers run trials on the various monitoring devices such as the copter that was guided by a GPS device to move up and down rows collecting data.

Matthews has been studying how deficit irrigation can be used to improve grape quality and that research is now being used in conjunction with the precision management study. “Our job is to present to the engineers grapevines with different known water status, and we’ve done that very well,” he said.

Matthews said the data collected with the new sensor equipment would be compared to results gathered with the traditional pressure chamber device that’s also referred to as a pressure bomb. Most growers can’t afford buying a pressure chamber, so Matthews said he’s hoping the study can offer an alternative that’s as accurate but more accessible.

Dr. Shrini Upadhyaya, a professor at UC Davis’ Department of Biological and Agricultural Engineering, is the project director. He said the team has not yet had a chance to analyze the data collected in the vineyard. “However we will be looking for interrelationships between canopy size, shape and spectral reflectance values with vine water status.”

He said the team used a sensor suite and leaf monitor to measure the stem water potential of grapes. “Our hope is that these units, which are primarily being developed for almonds and walnuts, may also be useful for grapes since the traditional method of measuring stem water potential using a pressure chamber is tedious and time consuming,” he said.

For other specialty crops, the question is often simply: Does the plant need water? Red winegrapes, however, are a trickier proposition as the question is not just is there a need for water but how much and when. “It’s when you want water stress, but not too much,” Matthews said.

Matthews evaluates water stress by collecting the grapes’ pH, acidity, tannin and anthocyanins levels and then produces small batches of wine to further gauge the effect of stress. By both tracking what type of deficit program yields the highest quality and good yields, Matthews can make recommendations for growers to achieve certain results. The monitoring system could help ensure that once a grower has picked an approach, he or she can achieve the desired outcome. “Ultimately, what we’re hoping is to be to do is make it very easy for growers to know the water status of the vineyard,” he said.

Is the system effective and affordable?
According to the project’s website, researchers will host field days in California and Washington in 2013 to discuss to the project’s findings and potential applications.

Upadhyaya said there are many individual sensors available to growers on the market but few interlinked systems. “We’re taking the components and putting together into a system,” he said.

He added that the team is also seeking input from growers about what type of sensors they may already be using and if the proposed system could be too complicated.

Part of the study includes an economic analysis to see if the changes in yield, quality and improved efficiency of a precision system justify the cost. “If the whole system works and let’s say we have a system that someone can put on the plant and it tells us its thirsty and someone can turn on the irrigation what is the cost of such technology that the farmer can afford?” Upadhyaya asked.