At bloom, if planted, germinated, and managed properly, a lot of underground biomass can be present. The grower (me!) had the 90%+ DU in Chico and used small spritz to keep things moving until the rain came. Photo taken at peak bloom for the nons.
Principle 7: What We Know and What We Don’t About Frost Principle: If it’ll make you sleep better at night, mow it. We need to know more about frost and cover crop, and growers should do what they feel is necessary to protect the crop and trees. You should also know that this is an ongoing research discussion with new, relevant data coming to the fore. Just imagine: what if cover crop can be shown to increase or hold heat that transfers to the canopy to reduce frost potentia l? There are a few things in the research community that we know about frost and susceptible almonds. First, frost risk
is greatest in nutlet stage after petal fall. 8 Second, cover crop, or any resident vegetation in the orchard rows for that matter, can reduce soil temperature compared to bare soil if not cut to two inches or below. This, in turn, can affect heat transfer. 9 However, new questions are being asked, mainly because growers seem to be experiencing different things when cover crop is left higher than two inches. 10 Furthermore, recent research from UC Davis has pointed out several interesting dynamics new to this discussion. Surface temperature in almond orchards with cover crop can be higher because the water in the cover crop
8 Connell, J. Almond Notes. UC Cooperative Extension. 15 February 2011. https://cebutte.ucanr.edu/newsletters/Almond_Notes74292.pdf. 9 Snyder, R.L., & Connell, J. (1993). Ground cover height affects pre-dawn orchard floor temperature. California Agriculture, 47(1), 9–12. https://calag.ucanr.edu/archive/ ? type=pdf&article=ca.v047n01p9. 10 Cf. Blue Diamon Growers’ Almond Facts July/Aug edition in 2022 to see our survey data given to us by growers about what they experienced with cover crop and frost this last season, https://bluediamondgrowers.com/wp-content/uploads/2022/08/Blue- Diamond_AlmondFacts_JulyAug_2022_web-A.ADAcompliant.pdf.
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SEPTEMBER–OCTOBER 2022
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