Pacific Nut Producer Magazine

Tag: deficit irrigation

  • September Orchard Tasks – Pistachios

    Pistachio harvest ended earlier than usual this year, but growers should not stop irrigating their orchards just yet. The early finish creates a longer post-harvest period before trees enter dormancy, making proper irrigation especially important.

    Research by Daniele Zaccaria, Mae Culumber and Anderson Safre of the University of California Cooperative Extension indicates that pistachio trees continue using water after the nuts have been removed. Although harvest is complete, evapotranspiration—the loss of water from the soil and through the trees’ leaves—continues until the trees become dormant.

    Because the post-harvest season will be longer this year, growers should continue monitoring their orchards’ water needs. Stopping irrigation too soon could place unnecessary stress on trees as they prepare for next season.

    However, the researchers suggest growers may be able to conserve water through carefully timed deficit irrigation. This practice involves applying less water than the orchard would normally use during selected periods. When managed properly, deficit irrigation may reduce water use by about 20% with little to no effect on the following year’s harvest.

    The key is timing. Growers should consider orchard conditions, soil moisture and the trees’ water needs before reducing irrigation. An early harvest does not mean water use has ended, and post-harvest management can play an important role in supporting the next crop.

    Read more about the research in the September issue of Pacific Nut Producer Magazine.

  • Managing Strategic Deficit Irrigation with a Pressure Chamber

    As we hit the final stretch of the growing season, effective management of strategic deficit irrigation can make all the difference between a stressful or successful harvest. Maintaining optimal tree stress for your current growing conditions as we approach harvest is critical, as too much stress can negatively impact kernel size and not enough stress can make it difficult to achieve a uniform shake.

    With that in mind, growers should look to the pressure chamber tool to understand the actual stress their trees are experiencing. While this tool can be used year-round, it’s especially helpful during this critical time of the growing season.

    Why?

    Because the pressure chamber is the     only tool that quantifiably measures water stress felt by your tress. Knowing your applied water, ground truthing and evapotranspiration rates are important factors to understand for thorough irrigation management, but without the pressure chamber you will get an incomplete picture of what’s really happening in the trees.

    Growers who are not familiar with using a pressure chamber may feel like it’s an overwhelming challenge to use it in the field. However ABC, through its online     Irrigation Station video series, has removed the guesswork of pressure chamber use for growers with a 3-minute episode demonstrating the basics of its operation. More detailed information on how to use a pressure chamber is also available on page 126 of the Almond Irrigation Improvement Continuum, a comprehensive manual of irrigation and scheduling practices, as well as in ABC’s latest irrigation resource, a one-pager that breaks down each step of how to use a pressure chamber.

    Using a pressure chamber will allow growers to effectively implement strategic deficit irrigation via the baseline method. Baseline values for pressure chamber readings have been calculated by the University of California using mathematical models, which have been validated through field experiments in almond orchards.

    A baseline value indicates how many “bars” a fully watered almond tree will read on the pressure chamber. One bar is equal to about 1 atmosphere of pressure or 14.7 psi. However, bar readings on the pressure chamber will vary depending on weather conditions such as temperature and air relative humidity. Growers should consult Table 2 on page 136 of the     Continuum for a baseline chart of readings under different weather conditions.

    It’s important to understand that irrigating to the baseline is not the goal with strategic deficit irrigation; rather, it’s about irrigating at what is called “bars below baseline.” It’s also important to note that the pressure chamber measures in negative bars of tension, so irrigating “below baseline”  will mean a higher reading on your pressure chamber gauge.

    Growers can watch the     Strategic Deficit Irrigation episode of The Irrigation Station for more information about irrigating at bars below baseline using a pressure chamber. —By Almond Board of California

  • Irrigation Tips to Mitigate Almond Hull Rot & Bark Damage

    The posting of this video is a little belated as almond harvest has already begun, but if you’ve had hull rot issues this season, be sure to watch this brief video interview with Nut Crops Advisor Mae Culumber as she provides some tips to prevent hull rot and trunk damage through better irrigation practices, as explained at a mid-July Nut & Vine Irrigation seminar at the UC Cooperative Extension office in Fresno.  Read more about it in Pacific Nut Producer Magazine.  Culumber will also be addressing almond growers at the Annual Grape, Nut & Tree Fruit Expo coming up on November 13th at the Big Fresno Fairgrounds, so be sure to attend!