Irrigation Strategies for Orchardists During the Water Shortage

Home News Irrigation Strategies for Orchardists During the Water Shortage

Posted on May 21, 2015

News_MicroSprinkler — Micro sprinkler systems can conserve considerable amounts of water in an orchard setting.

*Information in this article was adapted from a notice sent to area growers by Hood River OSU Extension Agent Steve Castagnoli

The Hood River Valley is experiencing one of the worst water years on record with the Hood River running 39% of normal, as of June 1st. The Mt. Hood snow survey site has 0 inches of snow water equivalent (there would be 48 inches on June 1st in an average year). As a result of these severe conditions, many irrigation districts will likely face water reductions and rotation schedules on all water users. At this time, we (and all local irrigation districts) are asking Hood River landowners to voluntarily reduce their water use by at least 25 percent.

For many, the water shortage will be an inconvenience. For farmers, it could affect their livelihood. Agriculture is a large economic base in the Hood River Valley and is dependent on irrigation for cropping. Farmers will need to accurately assess their water needs and increase their efforts to apply only enough water to maintain crops. Those that do not need to irrigate are encouraged not to.

Below are irrigation strategies that orchardists can use to increase their irrigation efficiency. Assistance is available through the Hood River Soil & Water Conservation District (SWCD), OSU Extension Service, and each irrigation district to help you determine how to improve your irrigation water management practices. The local irrigation districts can also guide you to efficient microsprinkler or drip systems that apply water at low rates. Grant and cost share assistance programs are also available through the SWCD and Natural Resources Conservation Service (NRCS).

Irrigation strategies for established orchards: For pears and apples, avoiding water stress during all stages of fruit growth will help achieve optimal fruit size and yield. Stone fruits (including cherries) have a more complex fruit growth pattern over the course of the season, which sometimes allows imposing deficits without affecting fruit size. Under our conditions, it’s probably not practical to do that, so from bloom to harvest, cherries may be treated similarly to pears and apples.

During most seasons, water stored in the soil from winter and spring rain provides adequate water for several weeks after bloom so it isn’t necessary to irrigate during that time. In much of the lower valley, we have recently reached the point where stored soil moisture has been depleted to a level where irrigation is needed. From now until harvest, your challenge is providing trees with adequate water while avoiding excessive irrigation or other inefficient irrigation practices.

One additional note about cherries: After harvest, tree water use is substantially reduced, so irrigation inputs can also be reduced. Todd Einhorn suggests that irrigating cherries after harvest at around 50% of preharvest levels should be adequate for continued normal growth and development.

Irrigation strategies for new plantings: With newly planted orchards, your main focus should be getting trees off to a good start by avoiding any stress due to inadequate irrigation, lack of nutrients, or competition from weeds. Small trees have very limited root systems compared to larger established trees. In newer blocks, you need to start irrigating earlier and irrigate more frequently. Irrigation sets should be shorter because you are managing a shallower root zone. Reducing water in late summer can help acclimate trees for fall and winter cold.

News_SoilMoistureMonitoring — Soil Moisture monitoring stations can help keep track of actual tree water needs.

WSU Irrigation Scheduler– irrigation scheduling made easier

A calendar approach to irrigating rarely matches crop water needs through the season. Using a systematic, information-based approach to irrigation scheduling will result in big improvements in efficiency and fruit production. Perhaps the simplest of these is a water budget approach where information about your soil, crop, irrigation system, and weather conditions is used to estimate crop water use and provide you with accurate information on irrigation intervals and set times.

Information on using the water budget approach is widely available in extension publications and basic irrigation text books. Even though it is fairly simple, using this approach may seem like more trouble than it’s worth because it requires record keeping and periodic calculations.

The good news is that there is free, web-based irrigation scheduling tool available through the WSU AgWeatherNet that will do all of the calculations for you. It provides automatically updated estimates of daily water use, available soil moisture, and water deficit values in either inches or set time equal to the amount of water you should apply to bring your soil to field capacity.

The WSU Irrigation Scheduler has many convenient features, including the capability to track several orchard blocks independently and access through your mobile device. You do need to set some basic initial parameters, but this requires minimal set up time. The Irrigation Scheduler uses daily weather data for the calculations. And, although this is a Washington-based system, it provides access to weather data from the US Bureau of Reclamation Agrimet system. We are fortunate to have four Agrimet stations in the Hood River Valley providing very good coverage for estimating water use under local conditions. In the Irrigation Scheduler these Agrimet weather stations are listed as Dee Flat, Hood River, Parkdale, and Pinegrove (Pine Grove).

Many of you have experience with Watermark sensors. These or other soil moisture monitoring tools are useful for seeing what’s happening in the soil and verifying results of water applied according to the Irrigation Scheduler. For information on using Watermarks, see this publication.

The Irrigation Scheduler is available free of charge, but first time users do need to register to create an account. To do that, visit the AgWeatherNet homepage. This Irrigation Scheduler user’s guide has information on getting started and the basics of the water budget approach.

Current and historical crop water use estimates can also be accessed through the Agrimet system.

An important aspect of managing soil moisture is the water holding capacity of your soil, which is dependent on soil texture. The USDA Web Soil Survey is a very useful tool for determining your soil type and water holding characteristics.