Effects of Subsurface Micro-irrigation on Water Use Efficiency and Hazelnut Tree Growth
Moisture losses associated with surface evaporation and weed growth under conventional surface irrigation methods, support research of highly efficient irrigation methods for producers to better conserve water and increase production efficiency. Drip irrigation is the most efficient method of irrigation but also has issues when used in orchards; tripping on the exposed lines, damage to the system from exposure to sunlight and rodents, concerns regarding the effectiveness of delivery of water and nutrients to the roots, and issues with plugged or non-flowing emitters that go undetected. Subsurface Drip Irrigation (SDI) puts the emitters underground eliminating issues with surface drip systems and micro-emitters. Benefits of SDI include the highest water use efficiency of any irrigation method reducing water use up to 40% while increasing yields and quality.
This project has three objectives: 1) determine the value of subsurface micro-irrigation on hazelnut tree growth; 2) define the best and most effective use of available irrigation systems for orchard crops; and, 3) evaluate the costs associated and best practices for greatest efficiency in water use for hazelnut growers.
This study, an extension of a previously funded SARE project, will clarify the advantages of this new irrigation method for growers coping with water scarcity in the western U.S., and gain a better understanding of growth capacities of hazelnut trees under water stress. The project will take place on a 13.4-acre hazelnut growing operation in the northern Willamette Valley of Oregon where 1,100 hazelnut trees have been planted in the last 4-years.
Education and outreach will include field days (pre- and post-harvest), irrigation in orchards “How-To” guide that will be distributed for free to orchardists in the region, articles in trade publications, and sharing the research results via social media outlets.
Overall goal: Achieve comprehensive understanding of subsurface micro-irrigation on hazelnut tree growth and hazelnut quality using minimal amounts of water to achieve acceptable nut quality.
Obj 1: Evaluate efficiency of our subsurface micro-irrigation strategy on water conservation
- Sub-obj 1: Calculate water saved without diminishing nut quality [Oct. – Dec. 2019/2021]
- Sub-obj 2: Compare different water use efficiency between subsurface micro-irrigation methods and surface drip irrigation [Oct – Dec. 2019/2021]
- Sub-obj 3: Determine combinations of water delivery amount and irrigation depth yielding highest water use efficiency [Oct – Nov. 2019/2021]
Obj 2: Measure the impact of our new subsurface micro-irrigation strategy on hazelnut growth and nut quality
- Sub-obj 1: Assess role of subsurface micro-irrigation strategies in hazelnuts quality [Mar.– Nov. 2019/2021]
- Sub-obj 2: Quantify subsurface micro-irrigation effects on hazelnut root distribution [Apr. – Nov. 2019/2021]
- Sub-obj 3: Analyze nutrient content in hazelnuts [Oct. – Mar. 2019/2021]
Obj 3: Educate hazelnut producers and engage community members on irrigation water conservation and hazelnut quality improvement
- Sub-obj 1: Conduct workshops to educate producers about improving hazelnut quality by using less irrigation water [Feb. & Aug. 2019/2021]
- Sub-obj 2: Develop educational materials for orchard managers and hazelnut growers to conserve irrigation water and improve water use efficiency [Jan. 2019 – Apr. 2021]
Because irrigation practices and their impact on growing operations and management practices are a result of many factors including seasonal and annual weather pattern changes, various irrigation methods may have simultaneous benefits and disadvantages, and measurements can’t be completed in a short study. Single year results do not provide an adequate evaluation of a cover crop’s potential (UC Davis Publication 3338). That is why multiple year experiments such as the one we are proposing are important to find out what works best with a given farm, its microclimate, soils, set of equipment, and other factors. In the case of long-term irrigation methods of hazelnut trees, benefits of each irrigation method may take several years to become apparent. For this project, education and outreach will include field days (pre- and post-harvest), irrigation in orchards “How-To” guide that will be distributed for free to orchardists in the region, articles in trade publications, and sharing the research results via social media outlets.
The project will take place on a 13.4-acre hazelnut growing operation on ZD Farms of Oregon in the northern Willamette Valley of Oregon where 1,100 hazelnut trees have been planted in the last 4-years. The orchard is broken into 5 irrigation zones of hazelnut trees ranging from 129 trees to 324 trees and ranging in age from 3-years to 4-years. The orchard has standard drip micro-irrigation systems supplying each tree with a single emitter and with drip supply tubing surface distributed. The project will include comparison of SDI and vertical watering pipes to existing drip system in the field designated Field 2 where 154 trees of the oldest variety are available and growing in the same soil type. 4 rows from this field, each with 27 trees will be selected, prescreened and 1 each row setup with SDI micro-irrigation, with 2 vertical pipe emitters per tree, with 3 vertical pipe emitters per tree and a control row with the existing drip system. Evaluation will be made on a quarterly basis for relative tree growth as well as core samples made for water displacement characteristics at the root level for each irrigation type. This layout of trees and irrigation variations allows for the various systems to utilize the same water source and soil type leaving the key variables to be in the irrigation methods allowing for more efficient project management and monitoring. There is also good vehicle access, plenty of parking, and field accessibility for our educational field days.
Educational & Outreach Activities
We will organize two field days at the research site. One field day will be post-harvest, taking place sometime in October of Year 2, another field day will be post-harvest, taking place sometime in October of Year 3. This will allow participants to look at the growth and also see how the management activities of the orchard irrigation has impacted tree development relative to each irrigation type. We will connect with both Washington State University and Oregon State University annual scheduled farm tours for inclusion in their stops. We will also work with the Hazelnut and Organic Hazelnut Associations to include their members in a tour of the research farm site as well as regional County extension and Soil Conservation Groups.
In addition, the project team will write and distribute two publications. One will be a lengthy and detailed final SARE report that will be available to anybody who asks to see it. The other will be a shorter, 2-3 page “how-to” guide written in non-academic language about which irrigation system options best meet certain growing conditions including benefits realized, costs of installation, equipment needed, etc. This shorter publication will be handed out at the field days and paper or electronic copies sent out to our regional Extension offices, conservation districts, and NRCS partners.
We will also actively cultivate trade media attention for this project by submitting articles and inviting journalists to write about it. Publications we will approach include the Good Fruit Growers magazine, the Capital Press newspaper, OSU Extension Orchardist e-newsletter, as well as spreading the word via select social media outlets. This will be especially helpful in getting the word out beyond our region to other fruit and nut growing regions of the country.
Table 1: Educational Outreach Timetable
Post-Harvest Field Day-October 2020
Post-Harvest Field Day-October 2021
Orchards Irrigation Options “How-to” Guide-Completed by October 2021
SARE Final Report-Completed by December 2021
Articles in trade publications-2020 and 2021
Social Media Outreach-2020 and 2021
Educational Materials to be Produced:
- Organize and deliver two field days at ZD Farms, estimating attendance of at least 100 farmers and agricultural technicians/educators in total. One field day will likely occur in Year 2 and one in year 3.
- Publish a 2-3 page cover crops in orchards “How-To” guide written in non-academic language to be distributed freely through farmer networks, at field days, through government agencies, and online. This will be written at the end of the three-year project in order to capture all of the data collected and interpret the results.
- Write annual progress reports and a more comprehensive final report for SARE, also to be made available to anybody who requests it, at the end of Year 3.
- Submit articles of approximately 1,000-1,500 words to the Good Fruit Grower magazine, Capital Press newspaper, and our local OSU Extension regional e-newsletter. Alternatively, ask their editors to write about our irrigation system research using information that we furnish to them. The media will also be invited to our field days. Years 2 and 3.
- Engage in social media outreach to disseminate the research information via Facebook pages of the farmer and partners, partner e-newsletters, orchardist online forums, and others. Years 2 and 3.
The project funds were received late in the growing season of 2019 which did not allow for installation completion until after the growing season was completed so no progress was made towards collection of data for each irrigation method. During this time, the following things occurred.
- installation of the 3 types of irrigation. 1) standard drip irrigation, 2) Deep drip PVC pipe irrigation, 2) DRI foam deep drip emitters
- final determination of the control valves and flow monitoring components for each test row. These will be installed Spring of 2020.
- measurement of each tree in the test. Measurements include height, condition and micrometer reading of each tree at a certain height for establishing a benchmark for each tree in the test.
Another key area of this project that needs to be addressed is the knowledge obtained within the installation process including tool requirements and time needed for installations. Due to the late start on the project into the hotter season, and as a result of the harder soil conditions in the orchard, the drilling of holes was more challenging than would have been in the earlier part of the season. This harder soil condition effected not only the time to drill each hole (2 holes per tree that required deep drip components) but it also impacted the longevity of the drill and drill bits used in preparing the holes for the emitters. Statistics were taken for the number of holes drilled and the time required to drill them throughout the process. Since some areas were even harder than others, in some cases the drilling could not be done in the ideal area and had to be moved around the permiter of the tree until a suitable area that would allow for the intended depth could be found, thus causing additional holes to be drilled for some locations. In the process 2 drill bits were broken at either the connecting point of the drill (the chuck) or at a point further down the drill shaft. Additionally 2 drills were damaged or overheated in the process of drilling and required purchase of other drills to complete the process.
For comparison, some of the pipes that were installed in locations that are less than desirable, will be re-drilled this spring when the soil warms and times will be kept for comparison to the times needed to drill in the previous year. The time comparisons will be reported in future reports.
As of this writing there have not been results to report as the project initiation was late in the 2019 growing season. Therefore zero project outcomes have been defined to date.
It is expected that future sustainable outcomes will include;
- reduction is water usage
- greater water efficiency through application of water directly to the root system.
- improved drought tolerance of the trees due to deeper root growth driven by more available water at the root system.
- improved fertilization or application of fertilizer to the tree root system; less fertilizer losses and/or less fertilizer benefit for weeds
- overall reduction is costs for irrigation and less impact on the local water supply.
To this date zero individual stories have been provided.
Initial installation challenges have identified that best practices to reduce labor, drill bit loss and damage to drill motors would be to do the installation work earlier in the season, likely early to mid-spring time. This adjustment allows for work in soil that is softer and easier to work.
More information is needed on hazelnut root development for the varieties growing in Oregon that can be related to any changing root development defined from this study project.
Near the conclusion of the project, the team will look for similar sized trees from each irrigation group to remove and evaluate the root stock variations.