Ag Alert September 9, 2020

Almond expert describes factors determining yields ByBob Johnson

not be productive long term unless the trees consistently grownew spurs. “The key to have good yields overmany years is to have a balance among the fruit spurs and the non-fruiting spurs, and among thedying spurs and thenewones,” Saa advised. “If we want towin this game, we need as many of these spurs as possi- ble. Almond spurs are alternate-bearing; they produce fruit one year and rest the next. Almond spurs are likely to die after bearingmultiple fruit, which is called the blackwidowphenomenon.” The number of spurs and flowers con- tributes greatly to yieldbut, he said, not all flowers are created equal. “The more flowers the better, but healthy and fertile flowers aremore likely to set fruit,” according to Saa. Management practices also play an im- portant role in determining howmany of the flowers set fruit. “Fruit set beginswith flowering, but that is just the beginning,” Saa said. “During bloom, fruit set is largely determined by thequalityof the flowers andby cross-pol- linationbetween thevariety thepollinizer. It is alsoaffectedby thenumber of healthy and strong hives.” Although the importance of pollination is widely known, less discussed is the role good plant nutrition plays in promoting healthy flowers and strong fruit set. “Boron plays a key role in the growth of thepollinic tube,” Saa said. “Zincaccumu- lates in the pollen and plays a key role in early cell division.” The trees will drop flowers and fruit to balance their load to the numbers of nuts they can carry. “Almond trees have three distinctive periods of fruit drop,” Saa said. “At flower- ing, amonth later, and six to seven weeks after bloom. That is when the trees sense howmuch load they have and drop fruit to adjust.” Though farmers cannot tell a tree how much fruit it can carry to maturity, they can influence thehealthandproductivity, he said. “Flowers are a game of numbers: the more thebetter,”Saasaid. “Irrigationman- agement is the key to overall tree health and the quality of the flowers.Waterman- agement has a dramatic effect onwhat we see today and also tomorrow.” Irrigation also affects the final compo- nent of yield, kernel weight; in one study, trees withwater stress inMay had kernels 20%smaller. ( 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.) Clarification A story in the Aug. 26 issue of Ag Alert® should have clarified that Farmers International Inc. of Chicohasnot directly experienced problems with overseas nut buyers beingunwilling topay theoriginal, contractprice foralmondsdelayedatports during the pandemic.

As almond farmerswalk their orchards, they should look at their trees in terms of a long-term relationship, according to Sebastian Saa, senior manager for agri- cultural research for the Almond Board of California. Before almonds flower and bear abun- dant fruit, they must produce spurs. And before that, the treesmust growthehealthy youngwood that produces those spurs. “More than80%of your fruit comes from almond spurs,” Saa said. “These spurs de- velop on 2- or 3-year-old wood. The trees have togrowthatwoodandthentheygrow the spurs, compacted shoots that are no more than 2 or 3 inches.” He made his remarks on the compo- nents of yield during a virtual meeting of the Almond Board, as a previously sched- uled In the Orchard workshop was con- ducted instead as a webinar attended by more than 200 farmers and pest control advisors fromaround the state. AccordingtoSaa, thethreefactorsthatde- termineyieldarethenumberof flowers, the percentageof fruitsetandthekernelweight. “We can put this as an equation: The yield is the number of flowers times the fruit set rate times the kernel weight,” he

Almond yield hinges on three ele- ments, says an Almond Board of California expert: num- ber of flowers, percentage of fruit set and kernel weight.

said. “More important than the actual number is knowing thehorticultural prac- tices that determine those numbers.” The goal of consistently producing an annual abundance of healthy flowers that are pollinated and set fruit that grows to a hearty weight informs virtually every op- eration in the orchard, Saa said. “When youwalk through your orchard, youhavefruitingandnon-fruitingspurs,”he said. “Thenon-fruitingspursareyour long- term investment; they will produce your cropnext year. Your yield this year depends on your fruiting spurs, but your yield next yeardependson thenon-fruiting spurs.”

A sound fertilizer program is one of the keys to producing a steady supply of new spurs to replace theones that dieafterpro- ducing flowers for a seasonor two, he said. “Nutrientmanagementhasadirecteffect onyourspurpopulation,”Saaadvised.“Zinc deficiency leads to reduced shoot growth, whichmeans less spur growth. Excessive nitrogen leads to higher susceptibility to hull rot,whichproducesa toxinthat cankill spurs. To keep balance, you should follow the four Rs: the right amount of the right material in the right placeat the right time.” Precise irrigation management, in ad- dition to affecting nut size in the current season, also impacts the number of spurs on the trees the following season. “If youapply toomuchor too littlewater, youcanaffect the sizeandperformanceof your spurpopulation thenext season,”Saa said. “The tree starts todecide in late sum- merhowmany flowers to formfor thenext season. Your irrigationmanagement inthe latesummerand fallwill affect thenumber and quality of flowers the next season.” The bottom line, he said, is that regard- less of the yield this year, the orchard will

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12 Ag Alert September 9, 2020