Posts Tagged: air quality

UC scientist studies an alternative to burning old trees when replacing an orchard

When almond orchards are about 25 years old, farmers must pull out the trees and plant new ones to maintain quality and yield. Typically, the old trees are pushed out and burned or ground up and hauled to a co-generation plant. However, UC Cooperative Extension advisor Brent Holtz believes there may be a better way.

Holtz has been pioneer in ag burn alternatives throughout his 26-year-career with UCCE, and going back still further on his family almond farm near Modesto. Beginning in the early 1990s, Holtz and his father experimented with chipping almond prunings instead of burning them, long before air quality regulations required wide implementation of the practice.

When Holtz heard a four-acre stone fruit orchard was slated for removal at the UC Kearney Agricultural Research and Extension Center in Parlier seven years ago, he took the opportunity to study the impact of grinding up and incorporating the whole trees before planting a new orchard.

“When an orchard is pushed out, there is about 100 tons per acre of organic matter that is taken out of the system,” Holtz said. “My previous research showed positive results from organic matter. Our San Joaquin Valley soils are typically critically low in organic matter. Why remove it if it is good for the soil?”

A local company was contracted to grind up and incorporate the trees using an Iron Wolf, essentially a 50-ton rototiller, in selected research plots. (See video below.) At first, Holtz was concerned that the Iron Wolf left “firewood-sized” chucks of wood in the plots, pieces much larger than he had studied before in his wood chipping research. But the worry turned out to be unfounded.

In comparison plots, trees were pushed together and burned. The ashes later were spread out on the soil. All the plots were fertilized at the normal rate.

Over the years, Holtz has compared laboratory analyses of the nutrients available to the trees in the soil and nutrients in the leaves. Initially, the burn treatments had more nutrients available. The second year, nutrient availability was about equal. Leaf analyses in the third year began to show a higher level of nutrients in the leaves of trees growing in the area where old trees had been ground up and incorporated. In the fifth and sixth years, Holtz didn't see any differences in growth, but data suggests slightly higher yields where the trees were ground up.

“A lot of growers feared if we added that much carbon to the soil, the microbes breaking down the organic matter would tie up nitrogen and the trees would be stunted,” Holtz said. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”

One potential barrier to grinding up old trees is the cost. Holtz said the Iron Wolf treatment cost $800 per acre and it is not readily available in the San Joaquin Valley. Burning is nearly cost-free for the farmer, but contributes to air pollution and is highly regulated.

Another option for almond farmers preparing to remove an orchard and replant is employing a large tub grinder, which leaves much finer particles of wood than the Iron Wolf, is more readily available but more expensive. Holtz said he hopes that growers in the future will receive incentives to grind up their orchards and incorporate the wood chips into their soils before they plant a second- or third-generation orchard.

“I'm trying to find growers who would be interested in trying this approach to conduct on-farm research,” Holtz said.

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In the video below, the Iron Wolf grinds up whole trees and incorporates the organic matter into the soil:

An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.

Study suggests air pollution is harming native plants, increasing fire risk in Santa Monica Mountains

Initial results from experiments conducted in the Santa Monica Mountains by a botanist at the University of California, Riverside and her colleagues indicate that high levels of nitrogen may adversely impact native plants and, by extension, increase the risk of wildfire.

The researchers measured atmospheric nitrogen deposition levels at ten sites throughout the Santa Monica Mountains and found significantly higher pollution levels in the eastern end, closer to Los Angeles.

Generally attributed to vehicle emissions in the Santa Monica Mountains, nitrogen deposition is the air pollution from industry, agriculture and transportation that settles out of the atmosphere and onto the earth’s surface.

The study is helping the scientists better understand how high nitrogen levels affect native vegetation and what that might mean for fire risk in such a fire-prone region.

“Invasive annual grasses from the Mediterranean have a greater growth response to nitrogen than most native species, and are crowding out native plants,” says Edith Allen, a professor of plant ecology and Cooperative Extension specialist at UC Riverside, and the principal investigator for the study. “Grasses also produce fine, flashy fuels that cause more frequent and larger fires, promoting vegetation-type conversion from native shrubland to exotic annual grassland.”

The preliminary results are from the first year of a three-year study undertaken by Allen, Irina Irvine, a restoration ecologist for Santa Monica Mountains National Recreation Area, and Andrzej Bytnerowicz and Mark Fenn of the U.S. Forest Service.

At the two sites with the best air quality, the researchers added various levels of nitrogen fertilizer into experimental plots of coastal sage scrub to simulate pollution levels found throughout the mountains. They found that the higher levels of nitrogen led to a decline in native shrub seedlings and an increase in nonnative grasses.

Other studies in Australia and California have demonstrated a link between nonnative grasses, also known as “flashy fuels,” and larger and more frequent wildfires.

“The recent fire of May 2013 burned our research plots, but provides an opportunity to learn how invasive grasses compete with native seedlings establishing post fire under nitrogen deposition,” Allen said. “The data will enable us to determine critical loads of nitrogen deposition to help set clean air regulations to protect native ecosystems.”

Coastal sage scrub once covered much of coastal California and is now an endangered habitat type, primarily due to development.

Funded by the National Park Service’s Air Resources Division, the $100,000 study will help the scientists better determine the “critical load” when vegetation shifts, causing alterations to the structure and functionality of ecosystems.

For more information, please visit: http://ucrtoday.ucr.edu/20098

 

Long-term study: Conservation tillage saves oil, soil and toil in cotton

A 12-year study published in the July-September 2012 issue of the University of California’s California Agriculture journal demonstrates that cotton grown in rotation with tomatoes — using lower-impact conservation tillage — can achieve yields similar to standard cultivation methods and at lower cost.

Conservation tillage seeks to reduce the number of times that tractors cross the field, in order to protect the soil from erosion and compaction, and save time, fuel and labor costs. Cotton crops are planted directly into stubble from the previous crop in the rotation.

In the study, conducted from 2000 to 2011 at the UC West Side Research and Extension Center in Five Points (southwest of Fresno), the number of tractor passes for a cotton-tomato rotation grown with a cover crop was reduced from 20 in the standard treatment to 13 with conservation tillage.

By the final years of the in the San Joaquin Valley study, cotton lint yields were statistically equivalent and even higher (in 2011) than with standard cultivation methods.

“The UC studies have consistently shown that conservation tillage can yield as well as standard tillage in a cotton-tomato rotation,” lead author Jeffrey P. Mitchell, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis, and co-authors wrote in California Agriculture journal.

Their study, “Conservation tillage systems for cotton advance in the San Joaquin Valley,” as well as the entire July-September 2012 issue of California Agriculture journal, can be viewed and downloaded online at: http://californiaagriculture.ucanr.edu.

Mitchell is a founder of Conservation Agriculture Systems Innovation (CASI), a diverse group of more than 1,800 farmers, industry representatives, UC and other university faculty, and members of the Natural Resources Conservation Service and other public agencies (http://ucanr.edu/CASI). CASI defines conservation tillage as a suite of cultivation practices — including no-tillage, minimum tillage, ridge tillage and strip tillage — that reduce the volume of soil disturbed and preserve crop residues in the field. Conservation tillage is common in other regions of the United States and parts of the world and is beginning to gain acceptance in California agriculture.

Technological upgrades to tillage implements have been critical to the advancement of conservation tillage systems. These include equipment that can target operations to just the plant row rather than the whole field as well as accomplish several operations at the same time.

Fuel use was reduced by 12 gallons and labor by 2 hours per acre in the conservation tillage plots. This amounted to savings of about $70 per acre in 2011 dollars.

Mitchell noted that more research is needed on the adequate development of cotton stands and the prevention of soil compaction under different conditions, but that the benefits of conservation tillage are becoming increasingly obvious. “Provided that yield performance or more importantly bottom-line profitability can be maintained and the risks associated with adopting a new tillage system are deemed reasonable, conservation tillage systems may become increasingly attractive to producers and more common in San Joaquin Valley cotton-growing areas.”

Also in the July-September 2012 issue of California Agriculture:

Agricultural burning and air quality: Southern California farmers in Imperial County regularly burn crop residues of bermudagrass in the winter and wheat stubble in the summer. A study of ambient air quality adjacent to and downwind of agricultural burning sites in the desert county found that particulate matter levels (PM_2.5) were 23% higher on burn days than on no-burn days at four locations. Researchers from the California Department of Public Health also assessed community educational needs regarding agricultural burning and developed fact sheets in English and Spanish targeting the general public, schools and farmers.

The value of privately owned oak woodlands: More than 80 percent of California’s 5 million oak woodland acres are privately owned. In a survey, researchers from Spain and UC Berkeley asked private owners of California oak woodlands to place a monetary value on amenities from their land such as recreation, scenic beauty or a rural lifestyle. The technique, called “contingent valuation,” found that landowners would be willing to pay $54 per acre annually for private amenities from their land and that their willingness to pay per acre decreased as their property size increased.

Microchips for woody plants: Radio-frequency identification (RFID) tags are widely used to track books in libraries, products during manufacturing, cattle from rangeland to the slaughterhouse, inventory in retail, runners in road races and much more. These tiny microchips (often the size of a grain of rice) are now being placed in woody plants such as grapevines and orchards to monitor crop diseases, track irrigation and pesticide applications, and help prevent the theft of valuable plants. In this review, Italian researchers discuss the emerging uses of RFID technology in agriculture.

Rainfall simulators to measure erosion: In their efforts to keep Lake Tahoe clear, researchers have been studying the movement of sediments into the lake using rainfall simulators. These fairly simple machines are placed on a slope; “rain” is created over a small frame, which allows sediment in the runoff to be collected and measured. However, the lack of standardization in erosion studies using rainfall simulators may be hampering progress. Mark Grismer, professor in the Department of Land, Air and Water Resources at UC Davis, makes the case for standardized field methodologies and data analysis.

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

WRITERS/EDITORS:  To request a hard copy of the journal, e-mail jlbyron@ucanr.edu.

Kern County UCCE hosts air quality study

A 60-foot tower near the UC Cooperative Extension office on South Mt. Vernon Avenue in Bakersfield has been built to hold instruments aloft for air quality studies in the area, the Bakersfield Californian reported.

Researchers from around the country are conducting the studies to gain a deeper understanding of the environment and to inform air quality regulatory policy.

"You need to measure what's in the air, and then from that you go back and look at crafting regulatory policy," UCCE farm advisor John Karlik was quoted. "But science has to precede policy."

The tower is hosted by the UC Cooperative Extension and funded by the California Air Resources Board.

Bakersfield was chosen as a site for the project, which began in May and runs through the end of June, because of its problems with air quality and its relatively strong sources of atmospheric compounds, the article said.

The participating scientists - representing UC Berkeley, University of Wisconsin and University of Miami - have already begun assessing data.

"It's all about how we put those data into a larger framework," Karlik was quoted. "We think it's of broader public interest."

Not a lot of greenhouse gas is from animal ag

There's been some confusion in recent years about the impact of animal agriculture on global warming. UC Davis Cooperative Extension air quality specialist Frank Mitloehner will share his findings on the subject this month during a free webinar on the eXtension website, according to an article in Pork magazine.

The 2006 United Nations report "Livestock's Long Shadow" said the livestock sector is responsible for 18 percent of greenhouse gas emissions, a higher share than transportation. Mitloehner said livestock's contribution is more like 3 percent, yet wide distribution of the misinformation has put Americans and others on the wrong path toward solutions.

The webinar, which will include information from Mithoehner's report "Clearing the Air: Livestock's Contribution to Climate Change," is at 11:30 a.m. Pacific Time June 11. Forum participants will have the opportunity to ask questions, post comments, upload photos and share their experiences. All the details, including links to background information and to the webinar, are in this eXtension flyer.

Black and white swine.

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