In response to water shortages in recent years, particularly on the West Side of the San Joaquin Valley, UC irrigation specialists and the Almond Board of California (ABC) have worked in concert to develop valuable Web-based irrigation resources summarizing past and current research. While this was in response to a crisis, these resources have ongoing value to almond production under all circumstances.

Twenty-five years of ABC-funded irrigation research have led to advances in irrigation scheduling and management, using drip or micro sprinklers, and deficit irrigation scheduling. This information is assembled on the ABC Web site http://www.almondboard.com/Growers/Pages/Default.aspx, and the path is: orchard management > water > Managing Irrigation for Optimum Efficiency > Drought, where you will find the following links:

• UC Drought Management – This site contains two sections quite valuable to almonds: UC Crop Irrigation Strategies for Almonds and UC Irrigation Scheduling.

• Almond Industry Conference, Dec. 11, 2008, Irrigation Strategies presentation.

• Almond Industry Conference, Dec. 10, 2009, Almond Irrigation World Round-Up, both presentation and audio files. You can open up both the PowerPoint and audio and follow the actual presentation.

In addition to the above links, you will find a host of valuable resources under both “Irrigation for Optimum Efficiency” and “Drought.” For instance, there are a number of presentations and resources on maintaining irrigation system efficiency, NRCS soil surveys and information on water holding capacity of different soils, and system and pump efficiency testing.

Lastly, ABC e-newsletters, dating back to January 2009, are available through the ABC Web site. Nearly every issue contains information on irrigation, often in the “Water Ways” feature. The path for the e-newsletter begins directly on the almond growers home page http://www.almondboard.com/Growers/Pages/Default.aspx > Current e-news.

Key points in the above resources:

• Ultimately it is the tree you are managing, so it is important to monitor tree water status using a pressure chamber as well as checking soil moisture and tracking almond evapotranspiration (ET). See UC Drought Management, Almond industry Conference December 2008 Irrigation Strategies, and January 2009 e-news.

• There are common pitfalls associated with not using all three of the scheduling techniques described in these resources. In high rainfall areas in normal years there is a tendency to over-irrigate in the spring and conversely, in low rainfall areas without these tools, there is a tendency to not irrigate sufficiently in the winter to recharge the root zone before bloom. See Almond Industry Conference December 2008 Irrigation Strategies, and January 2009 e-news.

• Deciding when to start irrigating in the springtime is one of the most important seasonal decisions and it should be based on plant (pressure chamber) and soil moisture readings. See Almond Industry Conference December 2009 Almond Irrigation World Round-Up “Benefits of Irrigation Scheduling” by Bruce Lampinen.

• Regulated deficit irrigation for mature trees during hullsplit has several benefits: reduced hull rot, more uniform hullsplit, improved nut removal and reduced water consumption with no impact on the subsequent season’s yield. See UC Drought Management, Almond Industry Conference December 2008 Irrigation Strategies, and Almond Industry Conference December 2009 Almond Irrigation World Round-Up “Benefits of Irrigation Scheduling” by Bruce Lampinen.

• It is important to avoid significant stress during the period of bud differentiation for next year’s crop during the period of mid-August to mid-September. See UC Drought Management and August 2009 e-news.

As young orchards are developing to full canopy, maintaining a fully watered status is important for both canopy development and crop production. However, once full canopy is reached, there are no advantages – and actually some disadvantages – to keeping trees at the fully watered baseline throughout the season. Using a pressure chamber to measure tree water status, the fully watered baseline is -6 to -8 bars. For orchards that have filled their allotted canopy space, coming off of this by -2 to -3 bars has not had an impact on yield and avoids several problems, such as root rot, anoxia, hull rot, open shells that are more susceptible to navel orangeworm, wet soils during harvest conducive to mold, and bacteria and resulting food safety problems.

See Almond Industry Conference December 2009 Almond Irrigation World Round-Up “Benefits of Irrigation Scheduling” by Bruce Lampinen.

State-of-the-art irrigation scheduling is of little value if your system is not tested and maintained. There are numerous resources on the ABC Web site under both “Managing Irrigation for Optimum Efficiency” and “Drought.”

These irrigation resources were assembled in response to those experiencing water shortages, but are a valuable resource for all almond operations. Take this opportunity to evaluate your practices for the coming irrigation season.