Spinach Continued from Page 7
Imperial Valley, said downy mildew severity varies from year to year based on weather. In conventional or nonorganic spinach, they’re able to manage fungal infections with fungicides if needed. But in his organ- ic fields, Vessey said downy mildew can take a significant toll on yield because of limited control options. “You can walk by acres and not harvest them. It’s an issue, definitely,” said Vessey, president of Vessey & Co. in Holtville. Montazar’s trial at UC’s Desert Research and Extension Center in Holtville involved the heirloom spinach variety Viroflay planted on 80-inch raised beds. The crop was grown organically as it would be for the baby spinach market. The cooperating producer near Winterhaven grows conventionally for the bunching spinach market. In addition to sprinklers and buried drip, Montazar said they looked at surface drip the first year. Because of strong winds, the tape moved around on top of the beds and was judged to not be a viable option. In addition, the surface drip could be a prob- lem for growers since the drip lines need to be removed before harvest and could pose a food safety risk. During the next two seasons, Montazar compared sprinklers to three and four rows of drip tape per bed buried 1.5 to 2 inches deep.
Ali Montazar, right, a University of California Cooperative Extension irrigation and water management advisor for Imperial, San Diego and Riverside counties, conducted trials on whether shifting spinach irrigation from sprinklers to drip irrigation could reduce the prevalence of spinach downey mildew, shown above. Drip irrigation produced a three-to- five-fold reduction in downey mildew compared to spinach fields using sprinkler irrigation.
The region’s loamy to silty clay-loam soils have good water-holding capaci- ty and substantial lateral water move- ment, so Montazar said four drip rows per bed weren’t needed. That’s why he eliminated the treatment the fourth year of the trial. But in sandier soils, he said the added drip line on an 80-inch
bed may be warranted. They also used buried drip to germi- nate the seed during the last two years rather than sprinkling the seed up and then switching to drip for the remaining 35 days. Montazar said the decision to focus only on drip was made because growers prob- ably wouldn’t use two different irrigation systems on such a short-season crop. Spinach biomass measured at selected times during the growing season did not vary significantly among treatments. One area where Montazar said they did notice differences was in downy mildew incidence. Even in the desert’s low humidity, he said they trapped downy mildew spores between December and February, which coincides with winter vegetable production. During the winter trials, they noted that sprinkler-ir- rigated plant canopies remained wet for 22% to 26% longer than drip-irrigated canopies. As a result, the drip-irrigated treat- ments had a three-to five-fold reduction
in downy mildew compared to sprin- kler-irrigated plots. Another difference Montazar said they saw was in time to get to harvest. Plants in the drip-irrigated plots took two to five days longer to reach the desired size compared to the sprinkler-irrigated treatments. “In all four trials, we observed this through infrared pictures,” he said. “It shows the can- opy for drip is behind two to five days. If you want to get the same yield, you have to go a little bit longer in the season.” Based on a sample cost analysis, Montazar said converting to drip irriga- tion from sprinkler irrigation for spinach is economically feasible. Vessey said he may consider buried drip for spinach. But he said he wants to look into it further and weigh the costs and ben- efits before deciding. After all, he said, installing buried drip is an added expense. (Vicky Boyd is a reporter based in Modesto. She may be contacted at vlboyd@att.net.)
Saving Farms Saving Profits Saving Futures
State soils, water programs to hold webinar on grants
Users of the Healthy Soils Program and the State Water Efficiency and Enhancement Program may provide feedback during a public listening ses- sion to discuss block grants as a poten- tial framework for disbursing funds. The California Department of Food and Agriculture is exploring a block grant program to allow flexibility, technical assistance and capacity building at the regional level. Under a block grant framework, qualified or- ganizations statewide may apply for state funding and administer award- ed funds to individuals for on-farm projects. Additionally, awarded or- ganizations would provide technical
assistance to individuals and ongoing grant administration support for se- lected on-farm projects. Entities that could be eligible for a block grant program include California-based nonprofit organi- zations, resource conservation dis- tricts, irrigation districts, groundwater sustainability agencies, air pollution control districts, universities and agri- cultural colleges, land trusts, and fed- erally and California-recognized Native American tribal governments. To access the webinar from 9 to 11 a.m., Oct. 10, register at https:// us02web.zoom.us/webinar/register/ WN_ze7qhvv0Tgq5ABquDWrFnA.
CHAPTER 12
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8 Ag Alert October 5, 2022
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