A SPECIAL GROWERS’ REPORT OF AG ALERT ® C A L I F O R N I A Trees & Vines ®
Crop consultant Cary Crum, left, discusses cover crops in a Madera County almond orchard. A webinar and orchard tour organized by the Madera/Chowchilla Resource Conservation District described use of cover crops and the attributes of different cover-crop varieties.
Cover crops could benefit orchards, specialists say ByDennis Pollock
harvest, “if well managed.” In addition, she said, therewill be newopportunities to skirt the clean-alleyways issue with off-ground harvests that are being discussed. Wauters said legumes decompose faster, and that cover crops canbe terminated after bloomby mowing or using an herbicide. She also said research has shown no negative impacts on yields and trends toward yield increase in very compacted orchards, an increase of as much as 225 pounds per acre in the second year of cover cropping. Wauters showed pictures that illustrated differences in the capture and conservation of winter rainfall in cover-cropped orchards inMerced. Cover crops were also found to result in a decrease in the amount of sodium con- tained in irrigation water. “Cover crops can be managed for pollinator resources without negatively affecting bee pollination services in almonds,” Wauters said, noting that it has been learned that flowers in orchard-adjacent wildflower plantings do not compete with almonds for bees. Diverse diets and longer sources of forage result in healthier bees, she said. Wauters said cover cropsmay pose less frost risk than conventionally thought, adding that varieties tested for cool-season cover inCalifornia include the Austrianwinter pea, balansa clover, black oat, cereal rye, crimson clover, daikon radish and hairy vetch.
Several people who are knowledgeable about cover crops gathered virtually for a webinar presentation on cover crops in orchard systems, presented by the Madera/ Chowchilla Resource Conservation District. That was followed the next day by visits to almond orchards showcasing cover crops inMadera and Chowchilla. Thewebinar’s lead-off presenter, JeffMitchell, with theUniversity of California, Davis, Department of Plant Sciences, is no stranger to the topic of cover cropping. For more than two decades, he has been pioneering use of covers and no or low tillage in field crops at the UCWestside Research and Extension Center in Five Points. He opened by describing market demands for farmers to pursue regenerative agri- culture. And he cited significant growth in tons of organicmatter and carbon as a result of cover crop use in Five Points. Mitchell, as he has in previous presentations, showed the differences in how water infiltrates soil with a cover crop, whereas it runs off places where there is no cover crop. That principle applies to both field crops and orchards, he said. Vivian Wauters, a postdoctoral researcher at UC Davis, discussed research updates on cover crops in almond orchards. She said cover crops do not necessarily interferewith the need for clean alleyways at
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May 26, 2021 Ag Alert 7
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