UC Food Blog
When it comes to watering walnuts, most California growers believe you need to start early to keep trees healthy and productive throughout the long, hot summer. But according to striking results from a long-term experiment in a walnut orchard in Red Bluff, growers can improve crop production if they hold off irrigation until later in the season and directly measure their trees' water needs.
The findings from researchers at the University of California may help farmers optimize water use.
“It's a game-changer,” said walnut grower Hal Crain, who welcomed researchers on to his orchard to test irrigation optimization. “It's clear to me you can improve nut quality and yield by applying water based on what the tree wants and needs, rather than just watering when it's hot outside and the soil is dry. That's a big deal for walnut growers and for the entire agricultural industry.”
Changing the paradigm
Crain is a second-generation farmer whose family has been growing walnuts in Butte and Tehama counties for 55 years. Like most walnut farmers, Crain had always started irrigating in early to mid-May when the days grew warmer and the trees sprouted leaves.
“That's standard practice for probably 90 percent of California's walnut growers,” said Crain, walking amid his trees on a sunny afternoon. “The theory is that when you irrigate early, you preserve the deep moisture in the soil that trees need to survive the heat of summer.”
But that's not how it works, the research shows. Instead, trees that grow in saturated soil early in the season don't develop the deep roots they need to thrive.
“With all the water right there at the surface, the lower roots suffer,” explained Bruce Lampinen, UC Cooperative Extension orchard management specialist with the UC Davis Department of Plant Sciences. “Trees end up with a very shallow root system, which doesn't serve them well as they try to extract moisture from the soil later on.”
Lampinen has long suspected that walnuts were getting too much water in the spring.
“A lot of the symptoms we see like yellowing leaves and various diseases can all be explained by overwatering,” said Lampinen.
So Lampinen did what scientists do: He set up an experiment. Five years ago, with funding from the California Walnut Board and the U.S. Department of Agriculture, he joined forces with Ken Shackel, a plant sciences professor with UC Davis, and Allan Fulton, an irrigation adviser with UC Cooperative Extension. Together, they led a team of scientists testing irrigation on Crain's ranch.
“Hal is an exceptional partner,” Fulton said. “Farmers have a lot to accommodate when they host an experiment like this, with researchers going in and out of the orchard at all hours. He had to work around our people and the timing of our water treatments. He's always eager to experiment with technology and learn new things, and he shares what he learns with other growers. Hal completes the circle.”
Tough nut to crack
When is the best time to irrigate? Researchers say the trees hold the answer. Scientists use pressure chambers, which are air-pressure devices that measure a leaf or small shoot to gauge how hard the plant is working to pull moisture from the soil.
“Just because the soil looks dry doesn't mean the plant is suffering,” said Shackel, who specializes in plant physiology. “Pressure chambers let you ask the tree how it's feeling — sort of like taking a human's blood pressure — which is a much more accurate way to measure a plant's water needs.”
For the last five years, the team has been applying different water treatments to five blocks of trees. One block is getting standard, early irrigation. Crain's orchard managers begin irrigating the other blocks when the trees reach different levels of water stress based on pressure-chamber readings.
The trees that experience moderate stress are doing the best. Their irrigation usually starts in mid-to-late June, several weeks later than when standard watering begins.
“You can tell just by looking at that block that the trees are healthier,” said Crain, standing beneath a canopy of lush, green trees. “And, we're starting to see greater yields and better nut quality.”
Translating the research
The research is helping scientists advise farmers on irrigation.
“My biggest take-away is knowing when to start watering is a really important factor to the health of your trees,” Lampinen says.
Pressure chambers — sometimes called pressure bombs — can cost more than $3,000, and high-tech versions are under development.
“I tell growers a pressure bomb would pay for itself even if you just used it once a year to determine when to start watering,” Lampinen said.
Crain is certainly convinced.
“When you irrigate based on your trees' needs, you optimize water,” Crain says. “I'm not using less water overall, but the water I do use is producing more food. That's good news for everyone.”
This story was originally published in the Fall 2018 issue of Outlook Magazine, the alumni magazine for the UC Davis College of Agricultural and Environmental Sciences.
Our friends the honey bees make it possible for us to devour an abundance of almond products. In 2016 the California almond crop totaled 2.15 billion pounds valued at $5.2 billion. Growing 80 percent of the world's almonds in California takes a lot of honey bees for pollination, roughly two hives for every acre of almond trees. It's estimated that California has 1.3 million acres of almonds, stretching 400 miles between Bakersfield and Red Bluff.
California is rated in the top five honey producing states in the nation. The U.S. per capita consumption of honey is around 1.3 pounds per year. Our buzzing friends visit millions of blossoms, making pollination of plants possible and collecting nectar to bring back to the hive. Lucky for us bees make more honey than their colony needs allowing beekeepers the opportunity to remove the excess honey and bottle it for us to enjoy.
Bees are animals too
Bees are one of our planet's most important animals. They produce honey and they are the primary managed pollinators for a majority of high value specialty crops grown in the contiguous states of California and Oregon, such as nuts, stone fruits, vegetables, and berries. A problem looms for our animal friends, the bees. Colony losses are high due to a variety of environmental and biological causes including bacterial diseases. Historically, beekeepers have self-prescribed antibiotics to control these diseases.
Enter UC Davis and Oregon State University to aid beekeepers in addressing the problem of antibiotic resistance and antimicrobial use in the feed or water of food-producing animals, namely, protecting the health and safety of bees. The overall strategy leads to a safer food supply because the potential for antibiotic resistance is reduced.
The Western Institute for Food Safety and Security (WIFSS), UC Cooperative Extension, and UC Davis School of Veterinary Medicine are partnering with Oregon State University in a USDA funded multi-state specialty crop project to develop CE training for veterinarians on bee health and antibiotic use — a practice that is now regulated under the Veterinary Feed Directive (VFD). The project will offer a comprehensive bee biology online course and train-the-trainer practical training for veterinarians and apiculture educators. The ultimate goals are to protect the specialty crop — honey — from becoming contaminated with antibiotic residues; to protect the health and safety of bees, which are essential to California agriculture; and, finally, to support veterinary oversight in the use of antibiotics, which will lead to an overall reduction of antibiotic resistant bacteria in the environment.
The $483,278 award will address the unique needs of the beekeeping industry that have been experiencing high colony losses since 2006. It will also focus on new rules established by the U.S. Food & Drug Administration on the use of antibiotics which are used to control certain diseases affecting bee colonies.
The principal investigator is Elina L. Niño, a UC Cooperative Extension specialist with the UC Davis Department of Entomology and Nematology. Project leader is Bennie Osburn, director of outreach and training at WIFSS. Collaborating in the project is Jonathan Dear, from the Department of Medicine and Epidemiology at UC Davis School of Veterinary Medicine, and the partner state collaborator is Ramesh Sagili from the Department of Horticulture at Oregon State University. A team of graphic and instructional designers from WIFSS will work with Drs. Niño, Dear, and Sagili, to translate the science into user friendly information for veterinarians and beekeepers.
Educating about honey bee health
Dear who is collaborating with WIFSS to produce an online and hands-on module to train veterinarians about beekeeping and honey bee health, points out that, “Honey bees are such an important part of our economy and, like any food producing animal, they can be affected by preventable and treatable diseases.”
He is enthusiastic about the project and says, “Our hope is that by educating veterinarians about honey bee health, they can play a key role in maintaining the health and wellbeing of this important species.”
With the efforts of extension specialists, veterinarians, and graphic and instructional designers, beekeepers and veterinarians will work together to navigate the VFD regulations, and consumers will continue to enjoy nature's sugar.
You may have heard the buzz about electric pressure cookers. Even if you don't follow kitchen trends, this piece of equipment may take some of the "pressure off" of preparing meals. From personal experience, I can say that they're also quite fun!
Pressure cooking vs. pressure canning
Pressure cooking uses trapped steam to create a pressurized environment for cooking food. This combined with heat can greatly decrease cooking times for many items. Foods like dried beans, meat roasts and rice can have a significantly shorter cooking time when they are pressure cooked. Some people may recognize the term pressure canning which uses pressure to preserve foods. While they are similar in the process, only equipment specifically labeled for pressure canning can be used safely for food preservation.
Why so popular?
Pressure cookers existed first as a stove top version that required manual monitoring of pressure. Electric pressure cookers arose to help streamline and simplify the process. They have digital settings and controls so are generally easy to use. The quick cooking time and ability to electronically set time and temperature also increase their consumer appeal. In addition, the cooker is a closed system which helps retain moisture, nutrients and flavor. Unfortunately, there is not a lot of scientific research on nutrient retention in pressure cooking. One study did find that pressure cooking retained more vitamin C in broccoli than compared to boiling or steaming.
Additionally, electric pressure cookers are more energy efficient than stove top or oven cooking. They are insulated which prevents energy from being lost in the cooking process.
Becky Hutchings, a family and consumer sciences educator for University of Idaho Extension, currently offers a very popular introduction to electric pressure cookers class in her community. She feels electric pressure cookers can help people save money and time with cooking. Hutchings has said, “I think with pressure cookers, people are scared that it's going to blow up. Once they use their electric pressure cooker they will realize how easy and fast it is. They wonder how they ever lived without it.”
As with any piece of equipment, there are safety concerns. Some models are considered “multi cookers” and may have a setting for slow cooking. This may be misleading as the slow cooker setting will not pressure cook. You cannot leave food in the cooker to be pressure cooked later because it will be in unsafe temperatures and will increase the risk for foodborne illness. For example, if you are planning to cook a pork roast in the electric pressure cooker, you cannot prepare it in the morning and leave it out on the counter until the evening. You will have to keep the food refrigerated until it is ready to be cooked.
Additionally, standard food safety practices should still be followed. Even if a roast looks done, check that temperature! Electric pressure cookers can be easily reset to cook for additional time if needed.
A third and significant concern is canning with electric pressure cookers. UC Cooperative Extension takes education on food preservation very seriously. We only support research-based and tested recipes for preservation. Many brands of electric pressure cookers provide recipes for canning. However, NONE of the brands have been able to supply their research or information supporting these recipes
The National Center for Home Food Preservation has a great article explaining why this is a concern. In short, electric pressure cookers have not been studied to ensure the necessary requirements for safe canning. Therefore, UC Cooperative Extension does NOT support or encourage canning in electric pressure cookers.
Hutchings explains it quite simply as “You are putting your life at risk."
Where to go from here:
While some models may be more “instantly” recognizable than others, there are many brands available for purchase. Just because a brand has popularity may not mean it is right for you. There are many online resources providing reviews and recipes for all the main brands of electric pressure cookers available. Prices of models range from $50 to $100. They are a more expensive piece of equipment, but savings could be seen in reduced cooking time and energy efficiency. In addition, there is a lot of money saved when cooking at home when compared to ordering delivery or eating at restaurants. An electric pressure cooker may be tool you need to making cooking at home easy and accessible.
If you are a new electric pressure cooker owner looking for support, Hutchings has a Facebook support group: Cooking Under Pressure - An Electric Pressure Cooking Community. She shares recipes, resources and occasionally hosts Facebook Live lessons.
Melanie Colvin, a graduate student at the UC Berkeley School of Public Health, focuses on addressing nutrition-related diseases through preventative measures. As a GFI fellow, Colvin will work with Nutrition Policy Institute researchers to conduct a secondary analysis of the Healthy Communities Study, a six-year observational study that included more than 5,000 children and their families from 130 communities in the United States. The native of Chapel Hill, NC, will analyze the relationship between household food insecurity and physical activity. Colvin plans to pursue a Ph.D. with a goal of a career in public health research.
"The GFI fellowship allows me to experience many facets of developing meaningful research questions that I will address on my own one day as a principal investigator," Colvin said.
“I am excited to learn from the UC ANR's Strategic Communications team and for the opportunity as a GFI fellow to gain hands-on agricultural research communication experience,” Mueller said.
In addition to their individual projects, the 2018-19 GFI fellows are invited to participate in systemwide activities designed to enhance their leadership skills and enrich their understanding of the food system in California.
The UC Global Food Initiative was launched by UC President Janet Napolitano in 2014 with the aim of putting UC, California and the world on a pathway to sustainability. The GFI fellows are part of a group of approximately 50 UC graduate and undergraduate students working on food-related projects at all 10 UC campuses, UC Office of the President, the Lawrence Berkeley National Laboratory and UC ANR. Each participant receives a $4,000 award to help fund student-generated research, projects or internships that support the initiative's efforts to address the issue of how to sustainably and nutritiously feed a world population expected to reach 8 billion by 2025.
Melanie Colvin, left, and Maci Mueller.
The transition of fall is upon us and gardeners are busy tending to late summer harvests, pruning back perennials, prepping for slower plant growth and more. But fall doesn't have to be all about wrapping up the growing season. In fact, life is sprouting and new garden plants are growing with the promise of fall, winter and early spring harvests.
Are you looking to join the cool-season gardening craze? The UC Master Gardener Program has engaging workshops to inform and inspire this fall. Bay Area residents can check out Growing Garlic and Onions in San Jose or Top 10 Vegetables for your Winter Garden in Campbell, both hosted by the UC Master Gardener Program of Santa Clara County. Another great resource is Saving the Harvest, a gardening and preserving guide and 2019 calendar created by the UC Master Gardener and UC Master Food Preserver Programs in Sacramento County. Check out the local offerings in your area at UC Master Gardener Program events.
Wherever you are in your gardening journey, here is a checklist of September activities for your garden:
- Maintain your warm-season garden with regular checks and harvesting. Prune new growth, flowers and any small or very immature fruits from tomatoes, eggplants and peppers. This practice encourages the plants to put energy into ripening fruit that has already set.
- Harvest and store seeds for next year's warm-season garden. To save and use seeds in the future, make sure you have a dry, cool location for seed storage. Don't forget to label and organize seeds to make preparation and planting easier in the spring.
- Remove and compost plants that have reached the natural end of lives or fruitfulness.
- Enjoy regular harvest of late-season-bearing cane berries like raspberries and blackberries. Check vines regularly for ripe fruit and pick before the birds steal away the fruit.
- Check and harvest edible landscape plants as well. Pineapple guava, Acca sellowiana, is a fantastic landscape shrub that has the added bonus of producing a tropical fruit. When pineapple guava fruit fall to the ground they are ripe, collect the fruits and wash, slice and eat the white fruit on the inside (like you would eat a kiwi).
By the end of the month it's time to start planting a cool-season garden. Try radishes and lettuces for harvest in late fall. They mature quickly and pair beautifully with roasted vegetables, cheese and nuts for a harvest-themed dinner salad. Broccoli and cauliflower are a great addition to your garden for winter harvest. Try roasting or making a creamy soup for a warm dinner on a cold night. Finally, onions and shallots are a must for your cool-season garden. They are slower to mature and will be ready for harvest in early spring to brighten your dishes and usher in a change in the seasons.
- Plant radishes, turnips, beets, onions and kale from seed.
- Pick up vegetable starts for broccoli, cauliflower, cabbage and lettuces at your local garden center.
- Keep soil moist while young plants send roots out into your garden bed.
- Provide shade to cool-season vegetables if needed to protect them from hot afternoon sun.
Connect with us
The UC Master Gardener volunteers are eager to help with all of your gardening needs. The UC Master Gardener Program can work with teachers and community volunteers to provide gardening information and consultation in the support of school gardens. With local programs based in more than 50 counties across California, there is sure to be a workshop or class near you. Visit our website to find your local UC Master Gardener Program, mg.ucanr.edu.
Missy Gable, Director of the UC Master Gardener Program shares tips for keeping a fall vegetable garden producing.