Posts Tagged: crops

Gene discovery may yield lettuce that will sprout in hot weather

A team of researchers, led by a University of California, Davis, plant scientist, has identified a lettuce gene and related enzyme that put the brakes on germination during hot weather -- a discovery that could lead to lettuces that can sprout year-round, even at high temperatures.

The study also included researchers from Arcadia Biosciences and Acharya N.G. Ranga Agricultural University, India.

The finding is particularly important to the nearly $2 billion lettuce industries of California and Arizona, which together produce more than 90 percent of the nation's lettuce. The study results appear online in the journal The Plant Cell.

"Discovery of the genes will enable plant breeders to develop lettuce varieties that can better germinate and grow to maturity under high temperatures," said the study's lead author Kent Bradford, a professor of plant sciences and director of the UC Davis Seed Biotechnology Center.

"And because this mechanism that inhibits hot-weather germination in lettuce seeds appears to be quite common in many plant species, we suspect that other crops also could be modified to improve their germination," he said. "This could be increasingly important as global temperatures are predicted to rise."

Most lettuce varieties flower in spring or early summer and then drop their seeds -- a trait that is likely linked to their origin in the Mediterranean region, which, like California, characteristically has dry summers. Scientists have observed for years that a built-in dormancy mechanism seems to prevent lettuce seeds from germinating under conditions that would be too hot and dry to sustain growth.

While this naturally occurring inhibition works well in the wild, it is an obstacle to commercial lettuce production.

In the California and Arizona lettuce industries, lettuce seeds are planted somewhere every day of the year -- even in September in the Imperial Valley of California and near Yuma, Ariz., where fall temperatures frequently reach 110 degrees.

In order to jump-start seed germination for a winter crop in these hot climates, lettuce growers have turned to cooling the soil with sprinkler irrigation or priming the seeds to germinate by pre-soaking them at cool temperatures and re-drying them before planting -- methods that are expensive and not always successful.

In the new study, researchers turned to lettuce genetics to better understand the temperature-related mechanisms governing seed germination. They identified a region of chromosome six in a wild ancestor of commercial lettuce varieties that enables seeds to germinate in warm temperatures. When that chromosome region was crossed into cultivated lettuce varieties, those varieties gained the ability to germinate in warm temperatures.

Further genetic mapping studies zeroed in on a specific gene that governs production of a plant hormone called abscisic acid -- known to inhibit seed germination. The newly identified gene "turns on" in most lettuce seeds when the seed is exposed to moisture at warm temperatures, increasing production of abscisic acid. In the wild ancestor that the researchers were studying, however, this gene does not turn on at high temperatures. As a result, abscisic acid is not produced and the seeds can still germinate.

The researchers then demonstrated that they could either "silence" or mutate the germination-inhibiting gene in cultivated lettuce varieties, thus enabling those varieties to germinate and grow even in high temperatures.

Other researchers on the study were: Post-doctoral researcher Heqiang Huo and staff researcher Peetambar Dahal, both of the UC Davis Department of Plant Sciences; Keshavulu Kunusoth of Acharya N.G.

Ranga Agricultural University, India; and Claire McCallum of Arcadia Biosciences, which provided the lettuce lines with variants of the target gene to help confirm the study's findings.

Funding for the study was provided the U.S. Department of Agriculture National Institute of Food and Agriculture and the National Science Foundation.

 

Working to achieve healthy crops while limiting nitrate in water

University of California Agriculture and Natural Resources is working to ensure that all Californians have access to safe drinking water and that the state’s farmers can grow enough food to help meet the world’s increasing demand. Research has shown that nitrogen fertilizer used in agricultural production can over many years move from a plant’s root zone into groundwater.

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. 

 

 

 

Rain-fed winter cover crops offer multiple benefits at low cost

Even on the west side of the San Joaquin Valley, where average rainfall is a mere 7 inches per year, farmers can reap the benefits of winter cover crops without the expense of irrigation, University of California research has found. Growing a winter cover crop helps retain soil nitrogen – keeping it from leaching into groundwater – improves water infiltration, reduces runoff, increases soil organic matter and boosts long-term soil fertility.

Moreover, a vigorously growing cover crop can smother winter weeds, reducing or eliminating the need for herbicides or tillage between crops.

“Despite the many and varied benefits of cover cropping that are increasingly seen by farmers in other parts of the country, the vast majority of Central Valley farmers currently do not use them,” said Jeff Mitchell, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis. Mitchell, a cropping systems expert, is based at the Kearney Agricultural Research and Extension Center in Parlier, Calif.

The costs and benefits of winter cover crops are being examined in an ongoing trial at the UC West Side Research and Extension Center in Five Points, Calif. Initiated in 2000, the trial is led by Mitchell, William Horwath, a professor in the Department of Land, Air and Water Resources at UC Davis, and Dan Munk, UC Cooperative Extension advisor in Fresno County, a cotton and soils expert.

Mitchell said the West Side trial addresses valley farmers’ primary concern about cover crops – water.

“When water is short, as it has been in many recent years, farmers wonder how inserting an extra crop that doesn’t bring an immediate return on investment makes sense,” Mitchell said. “But our work over the last 12 years has demonstrated that cover cropping ‘on the cheap’ – relying only on rainfall for irrigation – supplies many benefits and doesn’t cost much.”

Rainfall during the November to March winter growth period in Five Points averages 7 inches, slightly less than the 30-year average annual rainfall of 7.6 inches for the site. Winter rainfall has varied considerably during the trial, from a low of 2.9 inches in 2003 to a high of 11 inches in 2006.

From 2000 to 2010, a cover crop mix of triticale, ryegrain and pea was grown at a seed cost of $55 per acre (2012 dollars). In 2011 and 2012, the researchers used a mixture of fava bean and “tillage radish” for the cover crop, at a cost of $50 per acre.

Tillage radish is a large-rooted winter annual being marketed for its ability to improve soil condition. It’s thick, tuberous roots break up the soil surface. When it is killed in the spring and the roots decompose and shrivel, it leaves behind channels that help with aeration and water infiltration.

Over the course of the UC trial, an average of 3,400 pounds of dry biomass per acre was produced by the cover crops each year with rainfall alone. Productivity generally related to the amount of rain, with as little as 65 pounds of dry biomass per acre in 2007, when rainfall was 5.2 inches, and 6,400 pounds in 2005, when 10.1 inches of rain fell.

The timing of rainfall was also important. Rain is needed early to establish the crop and late in the season to sustain its growth when the temperature warms.

Over time, growing cover crops results in a significantly higher amount of carbon in the top foot of soil. Following eight years of cover cropping, soil carbon values in the standard tillage cover crop system, in which the cover crop was treated as a green manure and incorporated into the soil at a depth of 10 inches, was 12.2 tons of carbon per acre. Where cover crops were combined with conservation tillage, the researchers measured 12.8 tons per acre. In areas managed with conservation tillage and no cover crop, 11.7 tons per acre of carbon was in the top foot of soil. Under standard tillage and no cover crops, currently the common practice in the San Joaquin Valley, soil carbon came in at 9.9 tons per acre.

In addition to improving soil quality, farmers are investigating whether storing extra carbon in the soil will make them eligible for selling carbon credits under California Assembly Bill 32, the Global Warming Solutions Act.

“Sequestering carbon in farmland could be a means of mitigating global warming from greenhouse gas emissions,” Mitchell said. “We are working with farmers to develop a record of performance so they can document their potential for storing more carbon using conservation tillage and cover crops.”

Experimental field in which conservation tillage with and without cover crops are being compared to standard tillage systems.

UC receives more than $6 million for specialty crop research

University of California researchers will receive more than $6 million in funding from the U.S. Department of Agriculture’s 2011 Specialty Crop Block Grant program, which is intended to enhance agricultural markets, address environmental concerns, protect plant health, provide farmers with scientifically tested production techniques and increase food safety.

The USDA awarded $55 million nationwide for the Specialty Crop Block Grant program, which provides grants to states to enhance the competitiveness of fruits, vegetables, tree nuts, dried fruits, horticulture and nursery crops.

The California Department of Food and Agriculture identified 72 projects in the state for funding, including 30 projects led by University of California agricultural researchers.

“Funding for specialty crop research is critical to California’s $37.5 billion agricultural industry because many of the crops grown in California are considered specialty crops,” said Barbara Allen-Diaz, UC vice president for agriculture and natural resources. “With these funds, UC scientists will be helping California farmers find new ways to protect their crops from pests and diseases, remain economically viable, and provide healthy food for an increasing number of people.”

Highlights include:

• The UC Davis Center for Produce Safety received a combined $1.4 million for food safety projects, many of which will develop strategies to reduce the risk of foodborne illness.
• Assessing temperature conditions to determine the potential for using wind machines as an alternative to sprinklers for frost protection in coastal vineyards­ with the ultimate goal of reduced water use ­is the goal of a $59,961 project led by UC Cooperative Extension viticulture advisor Mark Battany in San Luis Obispo County.
• The UC Agricultural Issues Center will be conducting an analysis of the effects of quality control standards and European Union trade policies on the California olive industry, to identify market opportunities as standards and policies change, funded for $135,883.
• The largest single award made to UC in this round was $495,750 to a statewide project that will assess the effects of reduced irrigation on strawberries, blueberries and blackberries -- including berry yield, nutritional content, flavor and consumer preference -- ­led by researchers with the UC small farm program.
• A project that will train small-scale, Latino, Hmong and Mien growers in Fresno, the Sacramento Valley, the Central Coast and Southern California regions to compete in new markets, led by the UC Sustainable Agriculture Research and Education Program, received $86,851.
• Developing improved integrated pest management strategies that could help ornamental nurseries protect against the light brown apple moth is the goal of a $255,598 project led by Steve Tjosvold, UC Cooperative Extension farm advisor for Santa Cruz County.

“Many of these projects are collaborative efforts between farmers and scientists from UC campuses, UC Cooperative Extension advisors in counties, and other agencies and educational institutions,” Allen-Diaz said. “This array of expertise focused along the spectrum of specialty crops production will help keep California competitive in the global economy.”

For a complete list of California’s Specialty Crop Block Grants projects, please visit http://www.cdfa.ca.gov/grants.

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