Posts Tagged: Drought
Study finds using less doesn't compromise quality
California grape growers in coastal areas can use less water during times of drought and cut irrigation levels without affecting crop yields or quality, according to a new study out of the University of California, Davis.
The findings, published today (Sept. 1) in the journal Frontiers in Plant Science, show that vineyards can use 50% of the irrigation water normally used by grape crops without compromising flavor, color and sugar content.
It sheds new light on how vineyards can mitigate drought effects at a time when California is experiencing a severe water shortage and facing more extreme weather brought on by climate change, according to lead author Kaan Kurtural, professor of viticulture and enology and an extension specialist at UC Davis.
“It is a significant finding,” Kurtural said. “We don't necessarily have to increase the amount of water supplied to grape vines.”
Growers will also be able to use this information to plan for the next growing season. “Everybody's worried about what's going to happen next year,” he said.
Kurtural and others from his lab studied irrigation and cabernet sauvignon grape quality at a research vineyard in Napa Valley over two growing seasons, a rainy one in 2019 and a hyper-arid one in 2020.
They focused on crop evapotranspiration, which was the amount of water lost to the atmosphere from the vineyard system based on canopy size. The weekly tests used irrigation to replace 25%, 50% and 100% of what had been lost by the crop to evapotranspiration.
Researchers found that replacing 50% of the water was the most beneficial in maintaining the grape's flavor profile and yield. The level of symbiotic arbuscular mycorrhizal fungi, which help grapevines overcome stresses such as water deficits, was also not compromised. And the water used to dilute nitrogen application was also reduced, making the process more environmentally friendly.
The water footprint for growing grapes also decreased. For both the 25% and 50% replacement levels, water use efficiency increased between 18.6% and 29.2% in the 2019 growing season and by 29.2% and 42.9% in the following dry year.
While focused on cabernet sauvignon, most red grapes will respond similarly, he said.
“In the end, drought is not coming for wine,” Kurtural said. “There doesn't need to be a tremendous amount of water for grapes. If you over irrigate in times like these, you're just going to ruin quality for little gain.”
Members of Kurtural's lab — Nazareth Torres, Runze Yu, Johann Martinez-Lüscher and Evmorefia Kostaki — are also credited as authors.
University of California Agriculture and Natural Resources provided partial funding.
For more information, contact:
- Kaan Kurtural, Viticulture and Enology, email@example.com
- Amy Quinton, UC Davis News and Media Relations, firstname.lastname@example.org
- Emily C. Dooley, College of Agricultural and Environmental Sciences, email@example.com
Extreme drought is changing agriculture across California — and urban farming is no exception.
Many community farms and gardens cultivate land owned by city or county departments, schools and private landowners. Lucy Diekmann, a UC Cooperative Extension urban agriculture and food systems advisor in Santa Clara County, says that how those institutions handle rationing or surcharges set by water retailers makes all the difference for urban farmers. Diekmann co-authored a 2017 study looking at how urban agriculture in Silicon Valley was affected by the last period of extreme drought.
For example, priced-based water conservation strategies had very different outcomes depending on the landowner. Diekmann and her co-authors learned that three-quarters of Santa Clara County's community farms had their water bill paid by a project sponsor such as a nonprofit or school, and the sponsor absorbed the increased costs. On the other hand, one city-run community garden raised fees by 27% in one year to discourage water use. Some gardeners either left, dropped off the waitlist or chose smaller plots.
Diekmann and her co-authors point out that a major challenge for water management in urban agriculture is the lack of data. Many community farms and gardens don't have their own meters.
"We recommend that cities and counties subsidize the cost of meters, give financial support for installing watering systems that support conservation, and offer irrigation training," Diekmann said.
Because the water landscape is so uneven for urban farmers — usually in ways that benefit well-resourced groups — Diekmann and her co-authors also write that “affordable, consistent water prices for all UA (urban agriculture) users” must be part of all cities' urban agriculture policy portfolios.
You can read Diekmann's full study at https://www.tandfonline.com/doi/full/10.1080/13549839.2017.1351426.
You hear it every time drought returns to California: “Turn off the faucet when you brush your teeth.” “Collect shower water in a bucket before it warms up.”
While valuable, these tried and true drought resilience strategies can also deflect attention from the monumental challenges posed by droughts to natural areas, waterways, agriculture and people in California. Far-sighted and discerning management of the state's annual precipitation and groundwater is critical, particularly as droughts become more frequent due to climate change, said Faith Kearns, the academic coordinator of UC's California Institute for Water Resources.
“Like so many big societal problems, we don't want to get caught up believing individual actions alone will solve this problem,” Kearns said. “Conserving water in households can help people feel activated and certainly conserve some water. But, at the same time, it's not enough. We have big, systemic issues to deal with.”
Urban water use in homes, landscapes, schools and businesses amounts to about 10% of total developed water use in California, according to the Northern California Water Association. Irrigated agriculture uses 41%. The remaining 51% is used for water in rivers protected by state and federal laws as “wild and scenic,” water required for maintaining habitat in streams, and water that supports wetlands in wildlife preserves.
Traditionally, when surface water supplies for California farmers are cut during droughts, farmers pumped groundwater to bridge the gap. Over time, many of the state's groundwater basins have become severely depleted. In 2014, during a devastating five-year drought, the California Legislature passed the Sustainable Groundwater Management Act to regulate groundwater use in the state for the first time. The law aims for sustainable groundwater maintenance by 2040.
“We're in the implementation phase and local groundwater agencies are in various stages of developing and implementing sustainability plans,” Kearns said. “This is an opportunity for public participation to ensure all voices are heard in the effort.”
Of particular concern are underserved rural families who rely on wells for their household water. When the water table drops due to excessive pumping, the families can be left without water for drinking, washing and bathing. Small scale farmers often meet the same fate. Larger, neighboring farms may be able to drill deeper wells.
Wintertime flooding in permeable areas is one way groundwater can be recharged as it is used during the dry season. Getting access to water, developing infrastructure and flooding large farms will allow water to seep back into aquifers. Small-scale farmers can also be involved, said Ruth Dahlquist-Willard, the UC Cooperative Extension advisor to small-scale farmers in Fresno and Tulare counties.
“If there was a way to incentivize recharge on small farms, I think we could really contribute to groundwater management,” Dahlquist-Willard said. “It is not just about how we protect small farmers but also about how we involve them and have something that works for everyone's benefit.”
Fallowing land will likely be needed to meet the groundwater law's sustainability requirements. A 2020 report by UCCE specialist David Sunding and UC Berkeley professor David Roland-Holst, Blueprint Economic Analysis: Phase One Results, estimates about 992,000 acres of California farmland will go out of production, representing $7 billion in lost crop revenue and $2 billion in lost farm operating income.
The public can support smart and equitable water management by learning about decisions being made by their own local water providers and elected government representatives that impact the future of the California water supply. UC Agriculture and Natural Resources and its California Institute of Water Resources have gathered materials to serve as a starting point for understanding and advocating for sustainable water.
Listen to these episodes of the Water Talk podcast:
Find more on the UC California Institute for Water Resources website.
UC Master Gardener Francie Murphy was pruning the succulents in her San Diego front yard when an unfortunate accident catalyzed her commitment to communicating the dangers of toxic plants. She trimmed a stem on her drought-tolerant pencil milk bush and milky sap spurted into one eye, causing stinging pain.
“I tried to wipe it out, and in doing so got in both eyes. I was blinded. The pain was unbelievable,” she said.
A nearby friend rushed her to the emergency room where the doctor diagnosed chemical burns to her corneas and washed her eyes with two liters of saline water each. Murphy removed the plant from her garden, but saw it growing throughout her community.
“I knew we had to do something,” she said.
Drought-tolerant plants like cacti, yucca, agaves and aloes have adaptations to protect themselves from wildlife in search of the moisture within their leaves and stems. They have spikes or spines to ward off people and animals. Other plants don't have outward signs of danger. Fire sticks, also known as sticks on fire and pencil cactus and by its scientific name Euphorbia tirucalli, is a very popular succulent in frost-free areas. Its vertical growth habit and showy soft green to reddish-gold stems make it a striking landscape specimen. A native of southern Africa, the smooth, coral-like stems look deceptively harmless. The sap is toxic.
“Fire sticks should be planted far from walkways, in the back of the landscape, where you can see them, but not touch them,” said UC Cooperative Extension natural resources advisor Chris McDonald. “When trimming the plant, wear long pants, long sleeves and eye protection. If the plant is tall, consider protecting your face.”
After Murphy shared her story about these plants with other Master Gardeners, UCCE San Diego gathered a team and worked with colleagues to secure funding from the County of San Diego to develop a website and handouts to inform the community about readily available yet toxic drought-tolerant plants being planted into California landscapes.
The handout can be downloaded from the Plant Safely website (https://ucanr.edu/sites/PlantSafely/). The materials were quickly distributed to nurseries, garden events and Master Gardener help booths, such as at farmers markets, home shows and fairs, and other educational events. A key feature of the website is a database of nearly 100 plants (which can be found here) with photos and descriptions that explain how they are unsafe and how they can be used safely in the landscape. (https://ucanr.edu/sites/PlantSafely/Common_Names/)
Some common yet toxic landscape plants included in the database are:
“These potentially harmful plants are grown widely in many parts of California,” McDonald said. “It's important to promote drought-tolerant landscapes, and we must also do it in a way that preserves public health.”
View the UC Master Gardener video about safely planting fire sticks (Euphorbia tirucoli):
Scorching temperatures and parched earth are no match for the sorghum plant — this cereal crop, native to Africa, will remain green and productive, even under conditions that would render other plants brown, brittle and barren.
A new study published this week in the journal Proceedings of the National Academy of Sciences provides the first detailed look at how the plant exercises exquisite control over its genome — switching some genes on and some genes off at the first sign of water scarcity, and again when water returns — to survive when its surroundings turn harsh and arid.
“With this research, we are laying the groundwork for understanding drought tolerance in cereal crops,” said Jeff Dahlberg, UC Cooperative Extension sorghum specialist. Dahlberg, co-author of the study, is also director the UC Kearney Agricultural Research and Extension Center in Parlier, one of nine research and extension centers in California that are part of UC Agriculture and Natural Resources.
Dahlberg said researchers can use the knowledge gained from this project to search for drought genes in other cereal crops.
“That has implications for feeding the world, particularly considering changing climate and weather patterns,” he said.
The massive dataset, collected from 400 samples of sorghum plants grown during 17 weeks at Kearney, reveals that the plant modulates the expression of a total of 10,727 genes, or more than 40% of its genome, in response to drought stress. Many of these changes occur within a week of the plant missing a weekly watering or after it is first watered after weeks of no precipitation or irrigation.
Kearney is a 330-acre agriculture research facility in the heart of California's Central Valley, where field-scale, real-world research can be conducted on drought impact on plants and soil microbial communities. The climate is naturally dry throughout the summer, making it ideal to mimic drought conditions by withholding irrigation water.
“People have really shied away from doing these types of experiments in the field and instead conduct them under controlled conditions in the laboratory or greenhouse. But I believe that the investment of time and resources that we put into it is going to pay off, in terms of the quality of the answers that we get, in terms of understanding real-world drought situations,” said Peggy Lemaux, UC Cooperative Extension specialist in UC Berkeley's Department of Plant and Microbial Biology and co-author of the paper.
To conduct the research, the team cultivated sorghum plants under three different irrigation conditions — pre-flowering drought, post-flowering drought and controlled applications of water — over three consecutive years at Kearney.
Each week during the growing season, members of the research team carefully harvested samples from the leaves and roots of selected plants and set up a mobile lab in the field where they could rapidly freeze the samples until they were processed for analysis. Then, researchers at JGI sequenced the RNA in each sample to create the transcriptome data, which reveals which of the plant's tens of thousands of genes are being transcribed and used to make proteins at particular times.
Finally, statisticians led by UC Berkeley statistics professor Elizabeth Purdom parsed the massive transcriptome data set to pinpoint how gene expression changed as the plants grew and were subjected to drought or relief from drought conditions.
“We very carefully controlled the watering conditions, and we sampled over the entire developmental timeframe of sorghum, so [researchers] could actually use this data not only to study drought stress, but also to study plant development,” Lemaux said.
The researchers noticed a few interesting patterns in the transcriptome data. First, they found that a set of genes known to help the plant foster symbiotic relationships with a type of fungus that lives around its roots was switched off in drought conditions. This set of genes exhibited the most dramatic changes in gene activity that they observed.
“That was interesting, because it hinted that the plants were turning off these associations [with fungi] when they were dry,” said John Vogel, a staff scientist at JGI and co-author of the paper. “That meshed well with findings that showed that the abundance of these fungi around the roots was decreasing at the same time.”
Second, they noticed that certain genes known to be involved with photosynthesis were also turned off in response to drought and turned up during drought recovery. While the team doesn't yet know why these changes might help the plant, they provide interesting clues for follow-up.
The data in the current paper show the plant's transcriptome under both normal conditions and drought conditions over the course of a single growing season. In the future, the team also plans to publish data from the other two years of the experiment, as well as proteomic and metabolomic data.
Nelle Varoquaux and Cheng Gao of UC Berkeley and Benjamin Cole of JGI are co-first-authors of the study. Other co-authors include Grady Pierroz, Christopher R. Baker, Dhruv Patel, Mary Madera, Tim Jeffers, Judith A. Owiti, Stephanie DeGraaf, Ling Xu, Krishna K. Niyogi, Devin Coleman-Derr and John W. Taylor of UC Berkeley; Joy Hollingsworth, Julie Sievert and Jeffery Dahlberg of UC ANR KARE; Yuko Yoshinaga, Vasanth R. Singan, Matthew J. Blow, Axel Visel and Ronan O'Malley of JGI; Maria J. Harrison of the Boyce Thompson Institute; Christer Jansson of PNNL and Robert Hutmacher of UC ANR.
This research was funded in part by the Department of Energy (DOE) grant DE-SC001408; the Gordon and Betty Moore Foundation grant GBMF3834; the Alfred P. Sloan Foundation grant
2013-10-27; L'Ecole NormaleSupérieure-Capital Fund Management data science chair and the DOE's Office of Biological and Environmental Research grant DE-SC0012460. Work conducted by the DOE JointGenome Institute is supported by the Office of Science of the DOE contractDE-AC02-05CH11231.
- Dealing with Drought: Uncovering Sorghum's Secrets
- Berkeley to lead $12.3M study of crop drought tolerance
- Drought treatment restructures plants' microbiomes
- Microbes associated with plant roots could be a key to helping plants survive drought