Blue Diamond Almond Facts March-April 2021

Almond trees are very resilient and have survived an entire season with just eight acre-inches of available water in an entire season. However, as discussed above, returning to full production will take two years after 100 percent ET available following a year of extreme drought stress. Irrigate in the cooler hours (evening and night). This saves water vs irrigating through the day. Evaporation losses of 10–20 percent of applied water have been measured in UC research conducted in August in the Sacramento Valley. Short irrigation sets (less than six hr) lose more water by evaporation as a percent of water applied than longer sets. Consider limiting/eliminating water use of non-crop plants. This is particularly true for sprinkler or flood irrigated orchards where irrigation water reaches orchard middles. Growing those weeds doesn’t help your trees, although it may help reduce runoff and orchard access after rain or irrigation. Consult with your PCA about weed control options in row middles in micro-sprinkler irrigated orchards. For example, in a three year study, late April application of a low rate (1 qt/a) of surflan, incorporated with sprinkler irrigation, controlled summer weeds through harvest but allowed winter vegetation to grow, helping reduce winter rainfall runoff and fall equipment access. Removing vegetation in drip irrigated blocks may not provide significant water savings as drip hose (and irrigation water) usually stays in the herbicide strip away from vegetation in the row middles. Steady water stress is better than a “feast or famine” approach. There is no “most critical time” for full water availability when water is short and so no benefit to providing more water to the orchard at any one time of the year. In a three year study testing crop yield and tree health under different irrigation strategies with good quality water, the best yields came from uniform reduction in percent applied water throughout the season. Using these results, if 60 percent of annual irrigation water budget is available, the orchard should get 60 percent of normally applied water in each set through the season. If a 100 percent water year irrigation set is 24 hours, 3 5 M A R C H – A P R I L 2 0 2 1