Weather Continued from Page 13
quality traits. Smoke also reduces grape- vine water demand and should be taken into account when managing irrigation, he said. Kent Lund, UC viticulture advisor for Madera, Merced andMariposa counties, discussed growing degree days and plant growthmodeling. He began by emphasizing that human biology differs from plants and pests in the vineyard, in that humans maintain a steady body temperature and our bi-
ological development is also steady. Plants, however, don’t maintain a con- stant internal temperature. As their tem- perature changes, so does the speed of their metabolism. Lund said there is a minimal tem- perature below which the metabo- lism of a plant stops. For grapes, this is around 50 degrees. Above that tem- perature, the metabolic rate increases with increasing temperature. If humans responded the same way
plants do, Lund said, “you could turn up your heater during the first year of your child’s life, tomake themdevelop faster.” And, he added, “Then you could turn the AC up tomake your child’s toddler years pass slower.” When it comes to plants, in addition to the minimum temperature, there is also a maximum temperature at which the metabolism again slows or shuts down. Lund said growing degree days can be used to estimate a variety of events during the grape-growing season, as well as canopy size, crop coefficient and water use. Work done inWashingtonduring a pe- riod of more than 20 years found a strong link between degree days and bud break, bloomand veraison, he said, and studies done in Chile on table grapes showed an even stronger correlation between predictions and what was happening in the vineyard. Lund said growing degree days can be used to predict the timing of phenologi- cal events that include bud break, bloom and veraison. He said the models have some lim- itations. Those include the fact that phenological events differ for every variety. Those events are also going to be affected by cultural practices and vineyard health. Canopy size, and thus crop coefficient and water use, are af- fected by a large host of factors, and the models ignore excessive tempera- tures, Lund said. (Denni s Pol lock i s a repor t er in F r e s no . He ma y b e c on t a c t e d a t agcompollock@yahoo.com.)
A re l a t i ve l y recent add i t i on t o weather monitoring involves wildfire smoke, which can cause off-taste in winegrapes and slow r ipening and drying of raisin grapes. Zhuang said smoke significantly re- duces sunlight and slightly reduces air temperature. Grape canopies need sun- light for photosynthesis, to increase berry size, and to accumulate sugar and other
FOR BETTER SIZE AND COLOR IN TABLE GRAPES GO WITH AFRIKELP
Percentage of fully colored berries in 2 table grape varieties at first harvest. CA, 2018.
Effect of Afrikelp on size categories in Sweet Globe. CA, 2020. Afrikelp LG-1 Competitor
96.8%
80%
0% 20% 40% 60% 80% 100%
68.8% a
81.0%
Avocados Continued from Page 10
68.5%
60%
49.9% b
47.5%
40%
29.2%
pruning shears; one of the reasons we like to use mechanical pruners on poles is we can do it from the ground,” Filipe said. “It can cost anywhere from $200 to $3,000 an acre to prune. On average, we spend $600 to $650 an acre.” Part of the strategy is to prune once a year, at a time when damage to the trees and lost fruit can be minimized. “We choose to make larger cuts once a year,” Filipe said. “We like to prune from February to April. It’s early in the season, so we can open up the trees and get new budwood that season. If you prune in the winter, you can have frost damage.” The prunedwood is left on the orchard floor to serve as mulch, as part of a strat- egy to keep the ground moist, because avocados are shallow rooted. “We like to leave all the cuttings on the ground,” Filipe said. “We bring in a chip- per for the bigger cuts, but everything stays in the grove. We try to irrigate every other day, to keep the top 6 inches of the soil moist.” ( 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.)
23.3%
20.9% a
20%
7.9% b
0%
Flame Control
Flame Afrikelp
Alison Control
Alison Afrikelp
< 13/16
14/16
> 15/16
R&D department Afrikelp. CA, 2020
University of California, Kern county. Dr. Ashraf El-kereamy, 2018.
Control
Afrikelp
www.afrikelp-usa.com
14 Ag Alert May 12, 2021
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