Posts Tagged: crops
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.
That old adage takes on more meaning when you plant wildflower strips on your farm. Wildflowers add resilience to our farming systems by providing bees with habitat and food - pollen and nectar. And they're not just for honey bees. Many native bees, such as bumble bees and blue orchard bees, are important crop pollinators. Currently about a third of our crops benefit from bee pollination. This includes vegetables, fruit and nuts, as well as crops grown for seed production, including sunflower, melon, and carrot.
Farmers primarily rely on honey bees for crop pollination; generally two colonies per acre are needed. Honey bees are efficient pollinators, but with colony collapse and increasing colony losses, we must diversify our farming systems so we don't rely solely on honey bees.
Some important native bee crop pollinators include bumble bees, sunflower bees, squash bees, mason bees (blue orchard bees, which pollinate almonds, are mason bees) and leafcutter bees.
The benefits of native bees? Generally they forage on flowers earlier in the day than honey bees do, they tolerate more wind and cooler temperatures and often they're more efficient at gathering and moving pollen from one flower to another. Native bees also prompt honey bees to disperse more, resulting in more pollinator efficiency. All this is important for good pollination and crop production, especially for crops like almonds that bloom in late winter when the weather is more unpredictable.
Many native bees, including squash bees, nest in the soil, generally excavating chambers about 12 inches deep, where they pack cells with pollen for their young. Bumble bees often occupy vacated rodent holes. Leafcutter bees nest in woody cavities, often taking advantage of old beetle galleries. Discing and land clearing removes their nesting sites and potential food sources, but if you add wildflower plantings and hedgerows of flowering shrubs on your farm, that brings them back. Farms with strips of flowers along field edges have higher numbers of native bees than those that do not. Honey bees also benefit from better nutrition from flowers, strengthening their resiliency to pests, diseases, and pesticides.
A recent study, Pest Control and Pollination Cost–Benefit Analysis of Hedgerow Restoration in a Simplified Agricultural Landscape, published by UC Agriculture and Natural Resources (UC ANR) and UC Berkeley, describes the economic value of these plantings. Generally, a $4,000 investment to plant a 1,000-foot hedgerow of native California plants, takes about seven years to pay off from enhanced pest control and pollination services from natural enemies and bees (where honey bees are limiting). If cost-share funding is available from the USDA, this will reduce the investment cost for the restoration and time on returns.
Although habitat plantings are definitely beneficial, some farmers have expressed concern that these plantings will bring in more pests, including rodents, birds and weeds. However, current UC ANR studies show strips of flowers on field edges export beneficial insects into adjacent crops for enhanced pest control. The wildflower strips are too small to support large numbers of rodents or flocking birds that can damage crops (with the possible exception of ground squirrels and cottontail rabbits), and weeds requiring management are present regardless of field edge habitat.
Water? Although it's hot and dry out right now, many wildflowers do not need summer water. This includes Bolander's sunflower (great for songbirds like goldfinches, but the seeds should not be included in row crop mixes as they will cross-pollinate with our hybrid sunflower seeds), milkweed (great for monarch butterflies), vinegarweed, tarweed, gumplant, turkey mullein (doves love these seeds), and summer lupine. Bees, including natives and honey bees, thrive on these hardy flowers, especially now that the growing season is ending, and few crops are blooming.
Look for more information on wildflower and hedgerow plantings on the Hedgerow Hub website, , the Xerces Society website, and UC Davis fact sheet Habitat for bees and beneficials.
Networking is important too. A recent UC ANR survey showed that networking among growers, landowners, and conservation agencies is crucial in the adoption and implementation of new ideas, such as wildflower plantings.
Bottom line: Wildflower strips can ensure a healthy, sustainable food supply for crops that rely on bee pollination. “Bloom where you're planted” equals “Reap what you sow.”
Can you help fight the California drought by consuming only foods and beverages that require minimal water to produce?
To begin with, not all water drops are equal because not all water uses impact California's drought, the researchers explain.
So just what water does qualify as California drought-relevant water? You can definitely count surface water and groundwater used for agricultural irrigation as well as water used for urban purposes, including industrial, commercial and household uses.
And here are a few examples of what water is not relevant to California's drought:
-- Water used in another state to produce young livestock that are later shipped to California for food production; and
-- Rain that falls on un-irrigated California pastureland. (Studies show that non-irrigated, grazed pastures actually release more water into streams and rivers than do un-grazed pastures, the researchers say.)
In short, California's drought-relevant water includes all irrigation water, but excludes rainfall on non-irrigated California pastures as well as any water that actually came from out-of-state sources and wound up in livestock feeds or young livestock eventually imported by California farmers and ranchers.
Also, the amount of water that soaks back into the ground following crop irrigation doesn't count – and that amount can be quantified for each crop.
Comparing water use for various foods
I think you're getting the picture; this water-for-food analysis is complicated. For this paper, the researchers examined five plant-based and two animal-based food products: almonds, wine, tomatoes, broccoli, lettuce, milk and beef steak.
In teasing out the accurate amount of water that can be attributed to each food, the researchers first calculated how much water must be applied to grow a serving of each crop or animal product. Then they backed off the amount of water that is not California drought-relevant water, arriving at a second figure for the amount of drought-relevant water used for each food.
They provide a terrific graph (Fig. 3) that makes this all quite clear, comparing total applied water with California drought-relevant water used for the seven food products.
Milk and steak top the chart in total water use, with 1 cup of milk requiring 68 total gallons of water and a 3-ounce steak requiring 883.5 total gallons of water.
But when only California drought-relevant water is considered, one cup of milk is shown to be using 22 gallons of water and that 3-oz steak is using just 10.5 gallons of water. (Remember, to accurately assess California drought-water usage, we had to back off rainwater on non-irrigated pastures and water applied out of state to raise young livestock or feed that eventually would be imported by California producers.)
“Remarkably, a serving of steak uses much less water than a serving of almonds, or a glass of milk or wine, and about the same as a serving of broccoli or stewed tomatoes,” write Sumner and Anderson.
Still skeptical? Check out their paper in the January-February issue of the “Update” newsletter of the Giannini Foundation of Agricultural Economics at http://bit.ly/1XKZxxC.
UC Cooperative Extension and Agricultural Experiment Station researchers are working with growers on fertilizer management, irrigation efficiency and other farming practices to provide options for protecting groundwater, which serves as a primary drinking water source for many rural communities. The following are some examples of ANR research and extension projects under way. The scientists’ names are hyperlinked to their contact information.
Quick nitrate test guides fertilizer management
Michael Cahn and Richard Smith, UC Cooperative Extension advisors in Monterey County, and Tim Hartz, UCCE specialist in the department of Plant Sciences at UC Davis, have developed a quick test to measure soil nitrate in the field so growers can match fertilizer rates with plant needs. The test has reduced nitrogen-loading rates by an average of 70 pounds per acre in lettuce. On-farm demonstration trials have shown that by testing the soil, growers can reduce their fertilizer use by about 30 percent. Major growers in Monterey County, who manage a significant number of vegetable acres in the Salinas Valley, have begun using the quick nitrate test in their operations. For more information read the summary article on p. 5 and fine tuning article on p. 12 of Crop Notes.
Assessing plant nutrient status
Leaf sampling is a common method of determining when a nut tree has a nutrient deficiency. Patrick H. Brown, professor in the Department of Plant Sciences at UC Davis and Agricultural Experiment Station pomologist, and his colleagues are studying other ways of assessing plant nutrient status to help almond and pistachio growers manage fertilizer applications with more precision. For more information, see Crop Nutrient Status and Demand.
NBOT aids dairies in nutrient planning
The Nitrogen Budget Optimization Tool (NBOT) is a planning tool being developed for dairies by David Crohn, professor and UC Cooperative Extension specialist in the Department of Environmental Sciences at UC Riverside. NBOT is an algorithm that uses a daily time step to represent crop nitrogen demand, nitrogen mineralization and losses from leaching, denitrification and ammonia volatilization. Typical nitrogen application charts tell how much nitrogen a crop needs during the growing season, but they do not say when the crop will need it. With NBOT, dairy operators input information about the crop they are growing, how much they expect to harvest and when they can apply manures. NBOT’s output gives an idealized management strategy that helps dairy operators decide what they should do all year round.
N-Ledger software addresses nitrogen management
A software program under development by a team headed by Marsha Campbell Mathews, UC Cooperative Extension advisor in Stanislaus County, will help dairy operators and other farmers improve nitrogen management by calculating when nitrogen applied in manure is expected to be released from organic form into a form that the crops can use. Nitrogen applications are tracked, release rates are estimated and adjusted for expected losses, and the calculated total is compared to the expected daily crop need for nitrogen. The program helps the user choose an application strategy that will meet the crop’s needs and result in the least possible amount of nitrate in the soil during periods when it is vulnerable to leaching or other losses. For more information, see the UC Cooperative Extension in Stanislaus County Manure Nutrient Management website.
Adjusting field length can reduce irrigation levels
In his research on how dairy operators can reduce water applications to their crops, Larry Schwankl, UC Cooperative Extension specialist at Kearney Agricultural Research and Extension Center in Parlier, has found that allowing less water to percolate will reduce impacts on groundwater. With shorter furrows, water applied per acre was cut nearly in half. In addition, manure water is often added to fresh water as part of dairy irrigation and fertigation practices, so being able to reduce the applied water also significantly reduces the amount of nitrogen applied. For more information, see Schwankl's Irrigation Management website.
UC helps dairy industry manage nitrogen on the farm
It is common practice for dairy operators to use cattle manure as fertilizer for their silage crops. UC Cooperative Extension advisors throughout California routinely provide reliable information to dairy operators and consultants so they can efficiently manage nitrogen on the farm and comply with pending state regulations. This information includes how to install and calibrate flow meters, how to measure nitrogen levels in manure ponds, how much nitrogen crops need and when they need it, and how to properly sample the crops that are harvested to know how much nitrogen is being removed. “We’ve developed protocols to ensure accurate information gathering, and we can share these with the dairy industry,” said Carol Frate, UCCE advisor in Tulare County. For more information, contact a UC Cooperative Extension dairy advisor.
To see other ANR projects and publications aimed at limiting nitrate leaching, please visit http://ucanr.edu/News/Healthy_crops,_safe_water.
At 925 million, the number of hungry people in the world is unacceptably high.
To combat world hunger, many scientists are working on developing crops that can resist disease and withstand the elements, from drought to floods. One such scientist is Sean Cutler at UC Riverside, whose breakthrough discovery last year of pyrabactin has brought drought-tolerant crops closer to becoming reality and spawned new research in several labs around the world.
Pyrabactin is a synthetic chemical that mimics abscisic acid (ABA), a naturally produced stress hormone in plants that helps them cope with drought conditions by inhibiting growth. ABA has already been commercialized for agricultural use. But it has at least two disadvantages: it is light-sensitive and it is costly to make.
Enter pyrabactin. This chemical is relatively inexpensive, easy to make, and not sensitive to light. But is it free from drawbacks? Unfortunately, no. Unlike ABA, pyrabactin does not turn on all the “receptors” in the plant that need to be activated for drought-tolerance to fully take hold.
What does that mean? A brief lesson on receptors may be in order.
A receptor is a protein molecule in a cell to which mobile signaling molecules – such as ABA or pyrabactin, each of which turns on stress-signaling pathways in plants – may attach. Usually at the top of a signaling pathway, the receptor functions like a boss relaying orders to the team below that then proceeds to execute particular decisions in the cell.
It turns out that each receptor is equipped with a pocket, akin to a padlock, in which a chemical, like pyrabactin, can dock into, operating like a key. Even though the receptor pockets appear to be fairly similar in structure, subtle differences distinguish a pocket from its peers. The result is that while ABA, a product of evolution, can fit neatly in any of these pockets, pyrabactin is less successful. Still, pyrabactin, by being partially effective (it works better on seeds than on plant parts), serves as a leading molecule for devising new chemicals for controlling stress tolerance in plants.
Each receptor is equipped also with a lid that operates like a gate. For the receptor to be activated, the lid must remain closed. Pyrabactin is effective at closing the gate on some receptors, turning them on, but cannot close the gate on others.
Cutler and colleagues have now cracked the molecular basis of this behavior. In a receptor where the gate closes, they have found that pyrabactin fits in snugly to allow the gate to close. In a receptor not activated by pyrabactin, however, the chemical binds in a way that prevents the gate from closing and activating the receptor.
“These insights suggest new strategies for modifying pyrabactin and related compounds so that they fit properly into the pockets of other receptors,” Cutler says. “If a derivative of pyrabactin could be found that is capable of turning on all the receptors for drought tolerance, the implications for agriculture are enormous.”
So he and his colleagues continue their research on pyrabactin derivatives, having set their eyes on the prize: An ABA-mimicking, inexpensive and light-insensitive chemical that can be sprayed easily on corn, soy bean and other crops to help them survive drought – one effective approach to combating and preventing hunger worldwide. Imagine that!