Blue Diamond Almond Facts March-April 2021

IN YOUR ORCHARD TIME TO CONSIDER With spring comes a shift from helping the trees set a crop to growing/protecting what has set. Disease control can be less of an issue and insect/mite control moves into the spotlight along with delivering nutrients at the right rate, timing, and location. A drought year means adding extra emphasis on irrigation management to the list of practices to consider in March and April for many growers and PCA/CCAs. Irrigation: The overall water picture is not good. Initial surface water allocation numbers are small to zero, and major reservoir levels are well below historical averages (see reservoir levels at: cdec.water.ca.gov/resapp/ rescondmain). Even though it can be impossible to know how wells will perform in a year like this, early season irrigation planning should consider available resources for the entire season. Research results show season-long limited irrigation delivers better results than, for example, full water early followed by limited/no irrigation later in the season. Consider differences in rootstock, variety, orchard age and yield potential when determining the short- and long-term value of an orchard. When planning the irrigation season for each orchard with your CCA, the following research based information may be helpful. Resources/Tools : A very useful resource for irrigation planning in a drought year is the publication “Drought Management for California Almonds”. Download it, free, at anrcatalog.ucanr.edu/pdf/8515.pdf. Stem water potential (SWP), measured by a pressure chamber device (sources include: pmsinstrument.com/, soilmoisture.com/pwsc/) , is the current, proven, gold standard for monitoring orchard water status. Even if not used regularly to schedule irrigation, the pressure chamber is the best tool for spot-checking other irrigation monitoring methods/technologies. Also, SWP is a more accurate measure of tree water status under saline conditions compared to soil moisture or estimating crop water use (using ET). This is a critical point in a drought year, especially where only low quality (saline) irrigation water is available. See ucanr.edu/datastorefiles/391-761. pdf for a free, detailed publication on using the pressure chamber for irrigation in almonds (and walnuts and prunes). Research findings: One year of severe orchard water stress results in two years of major yield reduction (see table), even if full irrigation is applied the second year. This is because flower bud differentiation for next year’s bloom occurs around harvest, and fewer flower buds differentiate under severe tree water stress. Crop loss in drought hit blocks will mostly be in lower kernel weight in the drought year, but will be due to significantly fewer nuts the next year compared to trees with good water status in both years. Nonpareil yield per acre and kernel size count from a single year of imposed drought treatments (2009) followed by full irrigation on all treatments the following year (2010). Yields were not significantly different in Year 3 of the trial (2011). Research by Dr. Ken Shackel, UC Davis Plant Sciences Department, John Edstrom UCCE Colusa County (retired), Dr. Bruce Lampinen, UC Davis Plant Sciences Department, and Larry Schwankl, UC Extension Specialist (retired) and supported by the Almond Board of CA and Nickels Soil Lab (Colusa County). Irrigation treatment acre-inches* in 2009 2009 Yield (lbs/acre) 2009 Kernel size (#/oz) 2010 Yield (lbs./acre) 30.8" 2440 24 2260 7.2" 1890 28 1350 3.6" 2020 29 1010 0" 1030 40 320 * Does not include 7–9" additional water from winter storage (in soil) + rainfall in-season 3 4 A L M O N D F A C T S