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Flooding alfalfa fields has high potential for groundwater recharge

A rigorous field study in two California climate zones has found that alfalfa can tolerate very heavy winter flooding for groundwater recharge. The research was published online Jan. 16 in California Agriculture journal.

The alfalfa research is the latest in a series of projects studying the effects of using land planted with permanent crops – including almond orchards and vineyards – to capture and bank winter storm water. Such projects have great promise but also require collaboration across multiple jurisdictions and agencies. UC Agriculture and Natural Resources vice president Glenda Humiston has made groundwater recharge on working lands and open spaces a division priority and is working with water and land use leaders around the state to facilitate it through policy recommendations and cross-agency collaboration.

Flooding an alfalfa field for groundwater recharge. (Photo: Andrew Brown)

Groundwater is a critical water reserve in California, particularly during droughts when surface water supplies are low. Water slowly filled California's aquifers over tens of thousands of years. Beginning in the early 20th century and continuing in the present day, groundwater has been consistently withdrawn at a higher rate that it can be replenished naturally. In 2014, the California Legislature enacted the Sustainable Groundwater Management Act, which requires all critically overdrafted groundwater basins to have a groundwater sustainability plan in place by 2020. 

Flooding agricultural land during the winter, when surplus surface water is often available, is one promising strategy for replenishing overdrafted aquifers.

View a four-minute video about on-farm flooding for groundwater recharge on the UCTV Sustainable California channel. In the video, Professor Helen Dahlke discusses the work she and her fellow UC Davis researchers, UC Cooperative Extension advisors and specialists, and California farmers are undertaking to test the impacts of irrigating almond orchards in the winter to recharge groundwater.

For the alfalfa flooding research, UC Davis and UC Cooperative Extension scientists flooded two established alfalfa stands, one near Davis and one in the Scott Valley, Siskiyou County, during the winters of 2015 and 2016. The sites were selected because the soils in those areas have relatively high water percolation rates.

Integrated hydrologic science professor Helen Dahlke in an almond orchard being flooded for groundwater recharge.

“We found that most of the applied water percolated to the groundwater table,” wrote lead author Helen Dahlke, integrated hydrologic science professor at UC Davis.

The alfalfa endured saturated conditions in the root zone for a short time, but the yield loss was minimal.

Dahlke and her co-authors – USDA Natural Resources Conservation Service soil scientist Andrew Brown, and UC Cooperative Extension specialists Dan Putnam and Toby O'Geen and the late UCCE advisor Steve Orloff  – noted that the positive results of the alfalfa trial show tremendous potential for the state's groundwater basins. Using an index created by O'Geen that identifies the locations of California soils suitable for on-farm groundwater recharge, the scientists calculated the potential groundwater recharge. If all the suitable alfalfa acreage were flooded with six feet of winter water, and assuming 90 percent percolates past the root zone, it would be possible to bank 1.6 million ac-ft. of groundwater per year.

“For reference, the Oroville reservoir, second largest in the state, has a storage capacity of 3.5 million ac-ft.,” Dahlke wrote.

Leigh Bernacchi, program coordinator of UC Water at UC Merced, interviewed Helen Dahlke to get more details on groundwater recharge strategies for California. Read the Q&A on the UC Water Center website.

Additional reading:

Posted on Friday, January 19, 2018 at 8:41 AM
Tags: groundwater (15), Helen Dahlke (3)
Focus Area Tags: Agriculture Natural Resources

Trip Report

We had a road trip planned that got postponed until next year by the terrible fires. The only part that we did not cancel was a trip to Phoenix to surprise my long time friend on her 60th birthday. We flew in and weren't at all disappointed by the weather or the scenery. While I've been to Phoenix before, I have never been a tourist there.

My friend's husband said that one of her favorite things to do is to go to the Botanical Gardens on her birthday. He had gotten tickets for all of us.  I could barely contain myself!!!

The Gardens there has different displays and entertainment going on all year round. Since we we were there for Halloween, there was a Halloween theme and also art depicting "El Dia de los Muertes" with an ecological twist. The Gardens is a beautiful  display of native plants laid out in an easy to navigate pattern so that one can enjoy plants that thrive in the desert climate. Unfortunately, we missed the blooms on several cactus varieties.

The paths led us to the butterfly house. It was amazing! There were several types of butterflies in residence for us to ogle. There were plates of fruit slices for their dining pleasure and the garden was set up for more feeding and places for them to lay their eggs. The color scheme was planned to titillate their butterfly senses (and mine).  I left there with thoughts of how I could modify my garden to be more attractive to butterflies. While I doubt that the black butterflies will ever migrate through our area, we do have the beautiful monarchs to admire and help.

And yes, my friend was surprised to find us in her kitchen when she got home from work.

Posted on Friday, January 19, 2018 at 7:34 AM

A Rousing, Standing Ovation for Eric Mussen

As Extension apiculturist, Eric Mussen shared his knowledge of bees. Here he opens a hive for a group to show them the queen, worker bees and drones. (Photo by Kathy Keatley Garvey)

It was so well-deserved. Internationally known honey bee guru Eric Mussen, Extension apiculturist emeritus, drew a rousing, standing ovation on Jan....

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Posted on Thursday, January 18, 2018 at 10:53 AM

Ag leaders, scientists set priorities to prevent invasive pest threats to the environment and economy

The gypsy moth, an interloper from Europe and Asia, is threatening California's majestic oaks in Ventura County.

Invasive desert knapweed, which comes from Africa, has made its first North American appearance in in California's Anza-Borrego Desert, where it has started to crowd out native plants.

Asian citrus psyllids are slowly spreading the devastating huanglongbing disease in Southern California citrus.

River rats from South America, called nutrias, are munching voraciously on wetland plants in some areas of Stanislaus, Merced and Fresno counties.

These are just a few of the insects, weeds, animals and diseases that have entered the state of California from elsewhere on the globe, causing tremendous ecological damage and huge economic losses to agricultural crops, which ultimately affect every resident of California.

Based on historical data, a new invertebrate species establishes itself in California about every six weeks, on average. They don't all become serious pest problems, but many evade eradication efforts, disrupt carefully balanced integrated pest management programs, hijack sensitive ecosystems, and spoil valued recreational resources and urban landscapes.

A diverse group of university scientists, federal and state government representatives, county agricultural commissioners and non-profit organization leaders who are battling these pests converged at a summit in the state capitol Jan. 11 and 12 to coordinate their efforts, pool intellectual resources, and plot a strategy for protecting agricultural crops, natural resources, unique ecological communities, cityscapes and residential neighborhoods.

“We are a big, beautiful, special place, blessed with great weather and diverse geography,” said California Department of Food and Agriculture Secretary Karen Ross at the summit. “That means a lot to our many visitors – including pests.”

Glenda Humiston, vice president of UC Agriculture and Natural Resources, said research is a fundamental component of the fight against damaging invasive species.

Glenda Humiston, vice president of UC Agriculture and Natural Resources, which co-sponsored the summit, outlined the goals.

“We know that collectively, we have the tools and expertise to prevent invasive species from entering California, spreading and becoming established,” Humiston said. “I am so pleased with the numbers of people here today, and the expertise that you bring.”

A fundamental component of the fight against damaging invasive species is research, Humiston said, adding that the European grapevine moth in an apt example. The pest was detected in California's wine country in 2009, and later found as far south as Fresno County. A multi-agency collaboration responded quickly.

UC ANR academics studied the moth's biology, life cycle, host range and proven management practices. They developed a pest management program that relied on mating disruption with pheromones and application of carefully timed insecticides. In short order, the moth population plummeted, and the state was declared free of European grapevine moth, lifting a quarantine, enhancing farmers' ability to export its product, and preserving the communities' economic wellbeing.

“This multi-agency collaboration contributed to a successful, science-based response plan to a serious pest threat,” Humiston said.

She noted, however, that prevention is the best option.

“This is critical,” Humiston said. “Once the pests are here, they cost us millions upon millions of dollars to manage, not to mention the devastation and destruction inflicted on our crops, natural resources and the damage to local economies.”

In 2010, CDFA created a strategic framework for addressing California's ongoing invasive pest problems and potential future introductions. Successful implementation of the framework requires partnerships involving government from the state to local levels, the agriculture industry and commodity groups, non-governmental organizations committed to the environment, and researchers at UC and other universities.

UC Cooperative Extension advisor emeritus John Kabashima led a break out session on arthropods during the summit.

UC Cooperative Extension advisor emeritus John Kabashima was instrumental in bringing the summit to fruition. Kabashima, who retired in 2015, continues to lead a battle against invasive shot hole borer pests in Southern California. The insects, originally from Asia, are killing thousands of Southern California trees, and have the potential to kill millions of trees in urban areas, natural areas and even on farms in parts of the state as far north as Sacramento.

“We convened this meeting to bring together experts in the field and people who are feeling the impacts,” Kabashima said. “We're trying to start a 21st century invasive pest program that would then be implemented and funded to address the urgent issues before they cause any more devastation.”

Summit participants prepare to vote on most pressing invasive species' issues and best management strategies.

At the end of the two-day summit, the participants voted to decide the most pressing issues and best strategies to take forward to their agencies, coalitions, research groups, legislators and constituents. Key strategies that emerged were:

  • Analyze the economic impacts of invasive species management and the cost of “doing nothing.”
  • Develop and maintain statewide surveys and map high-risk surveys.
  • Increase funding to study invasive species' biology. 
  • Create a standing rapid response workgroup to guide response to new invasive species. Fund a rapid response emergency fund.
  • Enact regulations to control high-risk vectors, such as soil, green waste, gravel, forage, straw and firewood.
  • Formalize the Invasive Species Council of California (ISCC) and the California Invasive Species Advisory Committee (CISAC).

Mark Hoddle, UC Cooperative Extension biological control specialist and director of the Center for Invasive Species Research at UC Riverside, said the summit was a valuable part of the ongoing battle against invasive pests.

“It's good to see the number of agencies and organizations involved with invasive species issues,” Hoddle said. “I'm impressed with the energy in coming up with these priority lists.”

Summit outcomes will include sending recommended action items to the Legislature for funding consideration.

“Without financial support, many of the management tools that prevent unwanted incursions, find and monitor incipient pest populations, and develop sustainable, cost-effective management programs won't be possible,” Hoddle said.

View Glenda Humiston's opening remarks here: 

Posted on Thursday, January 18, 2018 at 8:21 AM

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