IN YOUR ORCHARD
TIME TO CONSIDER
It is important to manage your orchard to maximize kernel dry weight! Providing your trees with adequate irrigation and nitrogen are key inputs driving kernel growth and final weight. Hopefully you will have enough water this year to drive and build kernel weight. A free publication on ‘Drought Management for California Almonds’ is available at anrcatalog.ucanr.edu/Details.aspx ? itemNo=8515. Be on the lookout for premature water stress as we approach the hotter months of the season. Your orchard’s water demand could vary depending on the amount of rainfall received, the soil’s water holding capacity, tree canopy size, and the amount of irrigation water applied. Monitor soil moisture before irrigations to avoid over or under irrigation. Soil based options include tensiometers, gypsum blocks, or neutron probes. Pressure chambers are very accurate at directly measuring tree water status, www.pmsinstrument.com. A free publication on irrigation management with the pressure chamber is available at: ucanr.edu/datastoreFiles/391-761.pdf. Crop evapotranspiration (ET c ) is the sum of transpiration from leaves and evaporation from soil and is referred to as the crop water requirement, or orchard water requirement. In Dr. David Goldhamer’s irrigation scheduling chapter, in our UC Almond Production Manual #3364: • ET o from May 1–15 is 2.1 total inches (47.3 gallons/ tree/day) • ET o from May 16–31 is 2.5 total inches (51.2 gallons/ tree/day) o Seasonal cumulative ET c from March 16 – May 31 is 9.4 total inches • ET o from June 1–15 is 3.3 total inches (70.6 gallons/ tree/day) • ET o from June 16–30 is 3.3 total inches (72.3 gallons/ tree/day) o Seasonal cumulative ET c from March 16 – June 30 is 16.0 total inches.
David Doll has also published a nice article “Water use efficiency, irrigating for the highest crop per drop” on the Almond Doctor blog thealmonddoctor.com/water_use_efficiency/. Nitrogen (N) is the most common element we can apply to our tree fruit crops. Almond growth and productivity depend on the availability and uptake of N. Most fertilizer recommendations are based on making nitrogen available to our trees so that a N shortage does not limit tree growth or productivity. Efficient N management is important as we collectively reduce groundwater contamination while keeping our orchards productive. Nitrogen usage should be based on individual orchard’s cropping history (previous yields) and leaf and water analysis to determine N availability and potential sources. Dr. Patrick Brown and co-authors, recently published “Nitrogen Best Management Practices” with the Almond Board of California at Almonds.com. A removal and replacement rate of 68 lbs. per acre of N is recommended per 1,000 lbs. of kernels harvested per acre, when estimating annual N demand from crop load. Dr. Brown’s research effort, near Belridge in Kern County, determined more accurately efficient N use in productive almond orchards. In this study, applications of 275 lbs. of fertilizer N produced 3500–4500 lbs. of Nonpareil nut meats/ acre in 2009–2011. A higher rate of 350 lbs. N/acre/year did not produce more nuts than the 275 lb. N rate. Lower rates of 125 and 200 lbs. N/acre/year produced good yields but significantly less than the 275 lb. N/acre/year rate. Dr. Brown carefully points out that you can’t expect to increase yields by increasing N application rates; that N applications should replace the N removed in last season’s crop. Some ground water has elevated nitrogen levels, and you should take into consideration any N found in well water in developing your fertilization program. Several years ago, the well water at my family’s farm tested at 50 ppm nitrate (NO₃-). If I applied 3- acre feet of water
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ALMOND FACTS
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