Steam Continued from Page 7
weed between and within rows at the same time.” The time saved by using the autono- mous weeders that cultivate within the rows varied with the amount of weed pressure in the three fields where they were tested, she said: Field one had ex- ceptionally light weed pressure, and the autonomous cultivators did not save hand-weeding time. But in field two, with higher weed pressure, hand-weed- ing timewas reduced from11.1 hours per acre to 9.4 hours. The greatest reduction in hand-weeding time, from 16.9 hours to 9.9 hours, came in the most heavily infested third field. “Our autonomous weeders controlled about 85%of theweeds, compared to40% with a standard cultivator,” Mosqueda said. “The uncultivated seed line is the area of concern. Weeds between the plants are typically removed by hand.” Although advanced cultivatorsmay be the answer to more effective control of weeds after they emerge, Fennimore said steamcould become amore economical method of preventing emergence. “How do you get pre-emergent weed control that is compliant with organic regulations?” he asked. “Steam is the oldest method of soil disinfestation. The guys in Denmark have shown it can be an economical method of weed control.”
As they test steam treatment of soil to prevent weed emergence, UC Cooperative Extension farm advisors also look for ways to make the practice more economical.
The steady growthof organics in straw- berries has taken Fennimore back to the question of how to treat the soil before planting the crop. “The hand-weeding costs in organic strawberries have gone up a lot; it’s up to $3,700 an acre,” he said. Fennimoredidaseriesof steamtrialsata strawberrynursery inthemountainregion near theOregonborder, andincommercial fields in theWatsonville-Salinas area. He said steamwith or withoutmustard meal was as effective as fumigation with
chloropicrin in ridding soil of Verticillium wilt pathogens, and yields were compa- rable to fumigated plots. One promising insight coming from the trials, he said, is it looks as though steam and mustard meal have a syner- gistic effect when used together. “The steam looks like it releases bio- fumigant compounds from the mustard meal,” Fennimore said. ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.)
Treating just a shallow, narrow band of soil within the seed line makes steam more affordable, but Fennimore said he hopes to go even further in reduc- ing the time, fuel and money needed to use steam. “Spot steaming is something I would like to try,” he said. “You coulddo a 4-inch square and plant a vegetable in the spot. You would need precision equipment. Wewant it to be the cheapest; wewant to go faster and use less fuel.”
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Robotics project intends to streamline leaf sampling
To help farmers optimize water use, University of California researchers will test robots to collect leaf samples in fields. Researchers fromUCRiverside andUC Merced have received a grant for more than$1million fromtheU.S. Department of Agricuture to automate the leaf-sam- pling process. As part of the project, UC Riverside said the researchers are developing a robotic pressure chamber that can au- tonomously sample leaves and imme- diately test them on site to provide the most current data. Frequently updated data can help farmers better plan irrigation schedules to conserve water, optimize the time and effort spent by crop specialists assigned to determine and analyze leaf water po- tential, and help decrease some of the costs in the food-production chain, the university said. The leaf-sampling project will build upon an existing UC-developed sys- tem called Robot-Assisted Precision Irrigation Delivery, which travels along rows of crops adjusting irrigation flows according to sensor data. The new project will equip the RAPID base robot with a custom-made, robotic
leaf sampler and pressure chamber be- ing designed by UC Riverside research- ers, and pair it with drones that can sur- vey fields and direct the robot to areas of interest. “Using this process, growers could survey plants all day long, even in large fields,” said Stefano Carpin, professor of computer science at UCMerced. According to UC Riverside, the re- searchers plan to have the first set of au- tomated pressure chamber prototypes fabricated by next spring, and to evalu- ate their performance and refine designs in controlled settings during the spring and summer of next year. The research- ers said they expect to have a completed setup by winter 2022, so they can begin controlled field testing. “We have to be quick about it, because if we miss a peak growing season, we have towait another ninemonths for the next one,” Carpin said. “We’d like to be able to start testing next summer and test every summer, andwe need to be able to maximize the tests.” When all of the components have been designed, the research team said, the designs and code will be made open source, and all the data collected during the project will be made available to the scientific community.
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8 Ag Alert December 2, 2020
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