New UC research shows recycled water is suitable for Napa vineyards, but adds chloride to Salinas Valley soil.

Last year was California's driest on record, and we are now in our third straight year of drought. Growers have fallowed fields they can't irrigate, ranchers have sold cattle they can't feed, and the state wants cities to cut water use by 20 percent. The July–September 2014 issue of California Agriculture presents a special collection of original University of California research on water efficiency.

"This drought is unprecedented — we've never had such a lack of rainfall since we started keeping track," says Doug Parker, who directs UC ANR's California Institute for Water Resources and also leads UC ANR's Strategic Initiative on Water Quality, Quantity and Security. "Farmers are looking for ways they can stretch their water budget."

One way is irrigating vineyards with recycled wastewater from municipal waste treatment plants. California recycles only 7 percent of the 9 million acre-feet of urban wastewater produced per year, and the state wants to nearly quadruple that by 2030. Besides providing a source of irrigation water during drought, recycling water is cost-effective and reduces wastewater discharge to rivers.

To see if recycled water is suitable for use in Napa vineyards, UC Cooperative Extension researchers evaluated the quality of water treated by the Napa Sanitation District (NSD) as well as its impact on soil. They found that the quality of the recycled water was similar to that of other local sources of irrigation water. Additionally, in a vineyard that was irrigated with recycled water for 8 years, the soil did not accumulate salts or toxic ions, such as boron.

"Our work suggests that treated wastewater from the NSD is suitable for irrigation of vineyards over the long term," the researchers say.

One caveat is that the recycled water was relatively high in nitrogen. The higher soil nitrogen levels will be fine for many vineyards but, when needed, growers can easily reduce nitrogen by planting cover crops such as cereals and other grasses during the winter. 

 

Also in this issue:

Recycled water increases chloride in Salinas Valley soil

Most growers in the northern Salinas Valley have irrigated their crops with recycled wastewater since 1998, raising concerns about salt accumulation in the soil. New research shows that since the year 2000, only a small amount of sodium has accumulated in the 12-inch deep rooting zone. In half of the fields studied, chloride has accumulated to levels that could affect yields of strawberry plants and leafy greens such as spinach. This chloride buildup may be due to the recent lack of winter rainfall, which normally washes salts out of the root zone, and could be mitigated by improving drainage and avoiding soil amendments that contain chloride.

Reducing runoff from alfalfa fields

Accounting for nearly 20 percent of total agricultural water use statewide, alfalfa is California's thirstiest crop — large amounts of irrigation water can be wasted as runoff. New UC research shows that alfalfa growers can reduce this runoff to a comparative trickle by using a mathematical model that predicts the advance of irrigation water across a field in combination with wireless sensors that track the water's advance. This new approach also frees growers from checking the irrigation status of fields in person, saving time and labor.

Predicting which plants will invade California

Most ornamental plants are happy to stay in gardens, but some jump the fence, invading wildlands and crowding out native plants. California has a wealth of native plants, about 3,400 species, but is also plagued by more than 1,500 species of invasive plants, many of which were introduced by the horticultural trade. New UC research identifies 186 ornamentals that have invaded Mediterranean areas in other parts of the world, and so are at high risk of becoming invasive here too. This work could help focus further risk assessments of imported ornamentals, as well as help land managers identify which species to watch for in wildlands.

The entire July-September 2014 issue can be downloaded at http://californiaagriculture.ucanr.edu.

California Agriculture is the University of California's peer-reviewed journal of research in agricultural, human and natural resources. For a free subscription, go to http://californiaagriculture.ucanr.edu or write to calag@ucanr.edu.

Fresh fruits and vegetables are essential foods in a nutritious diet, but not everyone can afford or easily buy produce. As part of the local food movement, more and more people are growing food in neighborhood community gardens. While these gardeners are guaranteed fresh produce, a UC nutrition expert wondered how the cost of growing their own compared to buying from a store.

This month Susan Algert, UC Cooperative Extension nutrition advisor, published research that shows gardeners can save money by growing their own vegetables.

“Low-income people in cities may be able to improve their nutrition by eating fresh vegetables grown in community gardens,” said Algert, who works with UC Cooperative Extension in Santa Clara, San Mateo and San Francisco counties.

To better understand how community gardens affect the affordability and amount of food available, she recruited 10 gardeners in San Jose to weigh the vegetables they harvested from their community gardens during the spring and summer.

The most common crops they grew were tomatoes, squash, green beans, peppers, onions, eggplants and cucumbers.

The citizen scientist gardeners harvested an average of 0.75 pounds of vegetables per square foot, which is more than the 0.60 pounds of vegetables per square foot USDA calculates as the typical harvest from conventional farming.

Algert found that community gardens produced on average 2.55 pounds of food per plant over the four months. For the season, buying the same vegetables at retail prices would have cost $435 more. People saved more money by growing more high-value crops such as tomatoes and peppers that grow vertically and occupy less ground space, she learned.

“We know that community gardens can be an important source of fruits and vegetables for people who don't live near a grocery store or a farmers market,” said Algert. “This study shows that vegetables from community gardens can also be more affordable than buying from a store. That's important to people who live on a low or fixed income.”

The amount of money people save by growing their own vegetables will vary. “Our citizen scientists who worked on this study are all experienced gardeners,” she said, “A novice gardener would likely need training to get the same results.”

Currently Algert is studying the amount of food grown in backyard gardens of low-income families in San Jose.

“It's a wonderful collaboration of nutrition educators, UC Cooperative Extension small farm advisors, UC Master Gardeners, Santa Clara University and Sacred Heart/Catholic Charities,” said Algert.

Her research team is metering water usage to include in their calculations of the cost of growing the food. The UC Master Gardeners have provided soil, raised beds, seeds and drip irrigation to families who are eligible for CalFresh assistance, formerly called food stamps.

In addition to fresh produce, gardeners get some exercise. “Gardening is an excellent form of physical activity,” said Algert.

The study “Vegetable output and cost savings of community gardens in San Jose, California” is published in the July edition of the Journal of Academy of Nutrition and Dietetics at http://www.andjrnl.org.

The community garden study was conducted in collaboration with the City of San Jose's Parks, Recreation and Neighborhood Services Department, which manages 18 community gardens on 35 acres of land.

“A significant number of regions in California won't have groundwater available in another generation or two if we continue business as usual.” -- UC scientists Thomas Harter and Helen Dahlke

Nearly two-thirds of the state's water supply is currently being pumped from wells that are tapping into California aquifers.

In the special edition of California Agriculture released today (July 16), UC Cooperative Extension specialist and UC Davis professor Thomas Harter and UC Davis professor Helen Dahlke call attention to the stress being placed on California's aquifers as well as the catastrophic consequences of not having this hidden resource available in future droughts.

In the University of California's premiere journal for agricultural research, the groundwater experts make the following key recommendations:

• Groundwater is most effectively managed at the local or regional basin level, with support from the state.
• Local groundwater management entities must be given better tools, such as clear mandates to assess, measure, monitor and allocate their groundwater and control its extraction.
• The definition of groundwater sustainability can be set at the state level and translated into specific actionable thresholds that must be enforced locally, with a credible threat of state enforcement should the local efforts be unsuccessful.
• Much better data collection, analysis, reporting and data integration are needed to provide transparency, to support local management efforts and to properly inform the public. This requires much stronger planning and support within the DWR and SWB.

“Fundamentally, even more needs to be done," Harter and Dahlke write. "Local land-use decisions on urban and agricultural development, which have critical impacts on groundwater resources, must be consistent with groundwater management objectives. This will require significant communication between land-use and groundwater managers. Effective integration with water quality management and surface water management efforts, which are governed separately, is also required. And none of these efforts can occur without sustained funding through a mix of local and state sources.”

In their outlook article, Harter and Dahlke also explore one of the most promising ideas to protect our aquifers: groundwater banking.

The idea is that during storms or flood control releases, excess surface water could be directed from streams via existing water conveyance systems onto dormant or fallow agricultural fields, which would then serve as infiltration basins. Solutions need to be developed to add significant recharge to California's aquifers, often during relatively short periods when excess surface water is available. 

A 3-year project, funded by UC Division of Agriculture and Natural Resources, aims to look at the feasibility of such groundwater recharge activities by setting up pilot groundwater recharge field experiments, which would provide valuable data to address concerns about the costs and risks to crops, the influence these projects may have on groundwater levels and flows, and the possibility of recharging contaminated water or degrading groundwater quality by leaching contaminants such as nitrate from the vadose zone. Data collected could serve as a foundation for developing economic incentives at the local, state or federal level to acknowledge the landowner's service to the local community and California's water supply reliability.

To read their entire article, "Out of sight but not out of mind: California refocuses on groundwater,” and the special "Water efficiency" edition of California Agriculture, visit http://californiaagriculture.ucanr.edu and  http://ucanr.edu/repositoryfiles/cav6803p54-136027.pdf.

 

Further reading:

UC Cooperative Extension Groundwater Program http://groundwater.ucdavis.edu

Helen Dahlke's groundwater banking project http://dahlke.ucdavis.edu/research/groundwater-banking

California Water Action Plan: Improving Groundwater Management (links to state policy and emerging legislation) http://groundwater.ca.gov

California Department of Water Resources report to the Governor's Drought Task Force http://www.water.ca.gov/waterconditions/docs/Drought_Response-Groundwater_Basins_April30_Final_BC.pdf

California Water Plan Update 2013 http://www.waterplan.water.ca.gov/cwpu2013

Association of California Water Agencies Recommendations for Achieving Groundwater Sustainability http://www.acwa.com/sites/default/files/post/groundwater/2014/04/final_acwa-groundwater-sustainability-recommendations.pdf

UC Cooperative Extension advisor Glenn Nader believes two problems could add up to one win-win solution.

The California drought has ranchers desperate for inexpensive livestock feed. Air quality protection regulations that limit rice straw burning leave the rice industry with an abundance of typically low-quality straw to unload. Though it has rarely been done, Nader believes special treatment of rice straw will make it a nutritious cattle food. Two problems solved.

Nader will introduce producers to this new way to get through the drought at a meeting from 9 a.m. to 12 noon July 29 at the Veterans Memorial Hall, 525 W. Sycamore St., Willows, Calif.

When rice straw dries, its value as a forage declines dramatically. For 15 years, UC researchers have been trying to figure out why, but the reason for the significant change is not understood at this time.

“At one time, we thought the problem was silica in the straw,” Nader said. “We grew silica-free rice. That didn't work. We thought it was the crystallinity of molecules in the straw. We parsed apart the plant, and we still don't know.”

Ultimately, it was a rancher who suggested the scientists to put aside their desire to know why quality declines when rice straw dries and look for practical ways to get around it. Nader postponed his retirement to comply.

Normally, rice growers bale the straw two to four days after harvest. Nader and his colleagues instead baled the straw immediately after it exited the grain harvester. They stacked the green straw bales and covered them with a tarp to retain moisture and prevent spontaneous combustion. The result is a product they named “strawlage.” One worry is mold. The researchers found that treating the straw with propionic acid prevents fungus growth.

“We haven't figured everything out, but with the drought conditions as serious as they are, we feel the time is right to share our research with growers,” Nader said. “We invite producers to come to the meeting to see if this will work for their operations. Several producers who have already fed strawlage to their cattle will speak at the meeting about their experiences.”

Nader believes the UC research into using rice straw for livestock feed will be helpful throughout the world.

Asian farmers produce rice straw in great abundance and their livestock would benefit significantly if the farmers worked to maintain the plant's moisture until it reaches cattle feeding troughs.

The July 29 meeting will cover:

• Nutritional advantages of strawlage over rice straw
• The challenges of baling the straw at 50 to 60 percent moisture
• Additives to prevent mold
• How to stake and tarp strawlage
• The costs associated with the practice
• How cows that ate strawlage last year fared

“Our goal is to give producers information that will allow them to make rice strawlage during this fall's harvest,” Nader said. “Both cattle and rice producers are encouraged to attend.”