Organic trees fare well in research on almond yields ByBob Johnson
tilizer 400-2 was injected through the irri- gation system,” Edstrom said. “This was expensive, and organic treatment blocks were still nitrogendeficient basedonsum- mer leaf nitrogen levels.” Last year, researchersmadeaconcerted effort to rampuporganic fertilitywitha se- riesof fertigatedandshankedapplications. They included 30 pounds of liquid nitro- genthroughthe irrigationsysteminMarch and100poundsofnitrogeninfeathermeal that was shanked in late April. “Organic production was good, and summer leaf levels were up compared to previousyears, althoughright onthenitro- gen-deficiency threshold,” Edstromsaid. Thedifference in leaf tissuenitrogenbe- tween the conventional and organic trees in a July sample—2.52% to 2.20%—was measurable, despite a significant invest- ment in organic fertilizers. Pest damage fromnavel orangeworms was easier tomanage in the organic trees after a rigorous programof orchard sani- tation. Implemented at the beginning, it was supplementedin2020byamatingdis- ruptionprogramwithpheromone puffers throughout the block. Navel orangeworm damage to the or- ganic nonpareil nuts dropped from 2% to just 0.5% in the first year of the pher- omone program. See ORGANIC, Page 8
A 15-year-long comparison of organic and conventional almonds, grown side by side at theNickels Soil Lab inArbuckle,
ha s y i e l ded va luabl e in- formation on key challenges in organic nut production—
andwhat can be done about them. In the most recent harvest, the organic nonpareil trees produced good-sized ker- nels. Their yields were not too far short of nearbyconventional treesand, despite the absence of any pesticides, there were few rejections for quality issues. But most important is the informa- tion gathered by a team of University of California researchers about major dif- ficulties in making those plots econom- ically viable. “During the 15 seasons of this trial, organic production levels, disease man- agement, weed control and nitrogen fertility have been the most challenging issues,” said John Edstrom, manager at the Arbuckle research orchard when the trial was planted. “Recently, nitrogen nu- trition has eclipsedweed control and dis- easemanagement as the largest, sustained challenge to economically sustainable or- ganic production in this orchard.”
Almond orchards are seen at Nickels Soil Lab in Arbuckle. For 15 years, University of California researchers have tracked organic almonds grown side by side with conventional almonds.
The trial hasbeenona7-acreblock split between conventional and organic areas, both planted in a 3-to-1 ratio in nonpareil and the pollinator variety Fritz. In 2020, the conventional nonpareil trees approached 2,700 pounds an acre while theorganic treesyieldeda littlemore than 2,100 pounds, with kernels that were only slightly smaller. While the organic nonpareil trees pro- duced a respectable 85% of the yields of their conventional neighbors, that harvest came after considerable head scratching and expenditure on fertiliz-
ing the nitrogen-hungry trees. “Almondsuseroughly60 to70poundsof nitrogen per 1,000 pounds of kernel crop, the highest nitrogen use of any tree crop commonly grown in California,” Edstrom said. “Maintainingorchardnitrogenstatus while maximizing organic production is challenging and expensive.” Ten years ago, researchers began in- jecting various liquid organic fertilizers through the irrigationsystemandstopped broadcasting yard waste compost, which provides little nitrogen. “From 2011 to 2019, liquid organic fer-
4 Ag Alert September 8, 2021
Powered by FlippingBook