UC researchers studying irrigation needs of almond trees have found that moderate water stress during the period of bud differentiation for next year's crop, from about mid-August to mid-September, will have little effect on subsequent year's nut numbers, but severe stress during bud differentiation has dramatically reduced fruit set the following season. Therefore, growers on a limited water budget should have saved some water for this period to protect next season's crop.
This same research indicates that almond trees can survive with as little as 6-12 inches of available water (combination of stored in the soil profile and applied) over the course of the season. At this very low level of available water, it appears best to spread the applied water over the season as much as possible, including bud differentiation, in proportion to almond evapo-transpiration (ETc).
Irrigation system and application efficiency are critical to minimize water losses. This includes a good, maintained irrigation system. Growers on a limited water budget should opt for fuller irrigations at critical stages rather than smaller doses more frequently, to minimize surface evaporation losses.