Can less water grow better berries?

It might be pouring rain today, but soon enough California will be dry again. As demand for water for a growing urban population and for environmental restoration increases, farmers throughout the state are working to grow crops using as little water as possible, and UC is working with them.

"Water supplies are being constrained. Farmers are facing reduced access to water," said Shermain Hardesty, a UC Cooperative Extension specialist in the Department of Agricultural and Resource Economics at UC Davis.

A team of researchers, led by Hardesty, is in the middle of a three-year investigation into the effects of different irrigation levels on the quality, shelf-life, nutritional content, sensory quality and yield of some delicious annual and perennial crops. They're trying to learn if some of our favorite treats - strawberries, blueberries and blackberries - can be even more tasty if they're grown with less water than usual.

The research involves using some elaborate formulas for determining how much water is needed. UCCE advisor Richard Molinar, working with small farms in Fresno County, is irrigating small plots of strawberries with different amounts of water, some at 125 percent of the normal rate, some at 100 percent, and others at 75 percent and 50 percent of normal. In San Diego County, UCCE advisor Ramiro Lobo is doing similar research on strawberries and blueberries; UCCE advisor Manuel Jimenez is working with blackberries and blueberries in Tulare County; UCCE advisor Aziz Baameur is planting strawberries and blackberries in Santa Clara County, and UCCE advisor Mark Gaskell is studying blackberries in Santa Barbara County.

Once the berries are grown, they need to be tested - and testing means tasting in this project. The research team is holding tasting sessions to let the public judge which berries they prefer. If you've ever tasted a dry-farmed tomato, you might guess the answer. The first tasting session was held at the Davis Farmers' Market in June, with seven more coming soon at farmers' markets and grocery stores around the state.

Taste is a great quality to measure, but only one aspect of the study. Berries are already known for having a high nutrient content, but growing them with less water might give them even higher nutritional value. The team expects to find nutrition density to be highest at the lowest irrigation levels. To test this concept, UCCE specialists Elizabeth Mitcham and Marita Cantwell, experts in postharvest science affiliated with the Department of Plant Sciences at UC Davis, are doing nutritional quality analysis of the berries as they are picked.

Because they have to deal with so many variables, from weather to pests to unexpected competition and volatile prices, farmers are often called gamblers. Because of all these uncertainties, farmers are likely to try to control what they can. Research team member Lawrence Schwankl, a UCCE specialist in the Department of Land, Air and Water Resources at UC Davis, says that many farmers are currently over-watering many crops.

"Over-irrigation is cheap insurance, especially for such high value crops," he said.

He explained that more water tends to grow bigger berries. Since the harvest is not mechanized for berry crops, it takes as much effort to pick a small berry as a large berry, making more efficient use of the pickers' time and filling the basket more quickly if the berries are bigger.

Such a trade-off for the farmers! The public may decide that they prefer smaller berries with more taste, and the scientists may decide that smaller berries are more nutritious, but will it be profitable to grow better berries? It may depend on how much smaller, and on how much less water for how much better nutrition and taste. It may depend on the water rates, says Hardesty. She will be taking all of these variables into account to determine the potential impact on profitability of lower irrigation rates on berries.

The team, which also includes UCCE advisors Michael Cahn in Monterey County and David Shaw in San Diego, will report the results of their study to California farmers in the final year of the project. This project is funded by a California Department of Food and Agriculture Specialty Crop Block Grant.

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