Growing mustard plants on farmland destined for carrot and onion crops could suppress dust on windy days, according to Grant Poole, the UC Cooperative Extension agriculture and environmental issues farm advisor based in the Antelope Valley.
Dust suppression is especially important in the Lancaster and Palmdale desert areas, where rapid urban development is making blowing soil particularly problematic. However, dust suppression isn't the onlyreason Poole is studying the mustard cover crops.
He says mustard, a quick-growing, high bio-mass crop, not only covers the soil, when incorporated, it may improve soil fertility and suppress soil-borne pathogens, nematodes and weeds. Mustards, as well as many other Brassica plants, produce chemicals called glucosinolates. When mustard plants are incorporated into the soil, the glucosinolates are converted to isothiocyanates (ITCs), compounds well known to kill or suppress many soil-borne diseases, nematodes and weeds.
ITCs are similar in composition to methyl ITC, the active ingredient in the common synthetic soil fumigant Vapam.
Methyl bromide, the most common and effective soil fumigant, will be phased out by 2005. With the increasing tolerance of soil-borne pests to other synthetic soil fumigants, like Vapam, mustards may find a place in the vegetable crop rotation.
Mustard may be planted in the spring or fall and takes about 45 to 90 days to mature. Once adequate biomass is achieved during the bloom period, but before seeds develop, the plants are chopped, disked underground and irrigated, Poole said.
“The amount of biomass and the degree of chopping and incorporation are critical in getting the maximum biofumigation effect,” Poole said. “Severe chopping of plant tissue ruptures cell walls and allows for more rapid chemical activity and release.”
Last fall, Poole began evaluating several varieties of mustards in cooperation with Bolthouse Farms in Lancaster to determine their ability to suppress cavity spot of carrots and pink root of onions. The data on this preliminary research will soon be available, but Poole said his observations show a significant improvement in the soil quality of mustard cover crop plots over untreated control plots.
Poole's mustard research project is among the many he will conduct in the Antelope Valley to support local farmers. He took the farm advisor position in February 2002 after it had been vacant for 10 years.
“It might surprise people that agricultural production in Los Angeles County is on the upswing. At the same time, urban growth is on the upswing in LA's ag areas,” said Rachel Surls, the director of LA County UC Cooperative Extension. Surls, based in Monterey Park, is Poole's supervisor. “Even though the Antelope Valley might have lower agricultural production than areas in Central and Northern California, the issues our farm advisor must deal with are on the cutting edge due to ag's proximity to a growing population.”
Additionally, she said, high desert agriculture is unique. “Things that UC farm advisors and specialists are doing in other counties don't apply in the high desert,” she said. “Now we have someone dedicated to farmers growing crops with the winter cold, summer heat and very, very windy conditions typical in the Antelope Valley.”
Offers IPM advice
Poole, a Lancaster resident, is providing one-on-one consultations with farmers, offering advice on integrated pest management, developing degree-day models for local conditions, studying water conservation, teaching soil moisture monitoring techniques and working on alfalfa weed management.
He has already brought University of California researchers to the Antelope Valley, including UC Davis alfalfa specialist Dan Putnam, Siskiyou County small grains farm advisor Steve Orloff and Kern County irrigation and agronomy farm advisor Blake Sanden.