Pete W. Jacoby 1, R. Troy Peters 2, Sindhuja Sankaran 3, Lav Ramchandra Khot 3
1 Professor, Dept. Crop & Soil Sci., 2 Assoc. Professor, Dept. Biol. Systems Engineering., 3 Asst. Professors, Dept. Biol. Systems Engineering, Washington State University, Pullman, WA
Written for presentation at the Emerging Technologies for Sustainable Irrigation A joint ASABE/IA Irrigation Symposium Long Beach, California November 10 – 12, 2015 Poster Presentation
This poster presentation describes methods employed to increase water use efficiency in grapevines via microirrigation delivered sub-surface at depths ranging from 30 – 120 cm. The irrigation delivery system uses 1.27 cm (id) diameter PVC tubes inserted vertically into pre-drilled holes placed 45 cm either side of the vine trunk and in line with the dripline. A barbed connector with attached 15 cm length of 0.63 cm diameter tubing attached to a fixed rate drip emitter (2 L/hr) beneath a center drilled PVC cap secures the system in place and prevents exposure of the dripper to either atmosphere or soil. Plant root growth in response to wetting zone is quantified by periodic digital photography via a clear hard acrylic mini-rhizotron and camera system controlled by a laptop computer. Plant water stress is monitored by pressure bomb and auto-porometer, and compared to digital imagery obtained from a thermal sensing camera mounted on an unmanned aerial vehicle (UAV). While this technique is currently being used only for research to quantify physiological responses of the vine and its root system, its potential use in mature vineyards may permit more water efficient irrigation while reducing weeds and disease issues, as well as avoiding root pruning during installation and lessening problems from burrowing rodents impacting buried lines or clogging of emitters from contact with the soil. Published results are anticipated by 2017.
Authors: P.W. Jacoby, X.C. Ma, and J.R. Thompson
Poster presented at Ann. Meeting, Washington Winegrowers, Kennewick, WA, 2/7/2017
Our hypothesis is that subsurface irrigation applied directly into the vine’s lower root-zone can result in both greater water use efficiency and improved fruit quality over surface applied drip irrigation. A randomized complete block design with three replications of each treatment and a split plot design to compare pulse and continuous irrigation schedules were used with season-long deficit irrigation treatments at Kiona Vineyards in the Red Mountain AVA of Washington. During 2015-2016, over 800 vines received subsurface drip irrigation applied by direct root-zone (DRZ) delivery at depths of 1, 2 or 3 feet below ground via vertically installed hard plastic tubes. Subsurface irrigation was delivered as either continuous or pulsed application and compared to surface drip irrigation application on an additional 180 vines managed to meet commercial production and quality goals. Subsurface treatments received total irrigation amounts reduced to 60, 30 or 15 percent of the full seasonal commercial irrigation amount, but no significant differences were attributed to either depth of delivery or pulse application. During 2015, production from vines receiving these reduced rates yielded 90 % of commercial production while receiving 60% of the water and 70 percent at the lowest rate (15 % of water applied to the commercial plots). Vines receiving direct root-zone (DRZ) irrigation at rates reduced to 60, 30, and 15% of commercial drip irrigation (DI) produced individual clusters with higher numbers of berries, yet smaller in size, than did clusters from vines receiving full rates of surface drip irrigation. These preliminary findings suggested that the DRZ form of subsurface micro-irrigation may have potential to both conserve water and enhance fruit quality for producing premium red wines. Therefore, the experiment was repeated in 2016 and samples of grapes from subsurface irrigation treatments and commercially grown grapes were submitted for analyses by a private testing laboratory. Results from these analyses showed that acidity became progressively reduced below the 60% irrigation rate, while sugars (Brix), tannins, and anthocyanins all trended higher with decreasing rate of irrigation. These results are in line with the findings of other investigators who have shown benefits in grape quality and water savings through greatly reduced irrigation levels along with yield reductions and/or physiological impacts on vines. Results from our study provides evidence that use of efficient irrigation application such as DRZ could both sustain vines and produce grapes during drought conditions while yielding grapes with potential to produce premium quality red wines.
Jacoby, P.W. 2016. Direct root-zone irrigation in vineyards. In: WSU Viticulture and Enology Extension News, p. 8, spring ed. http://www.wine.wsu.edu/research-extension.
Water management is considered one of the most important means of achieving high quality wine grapes (1). Most wine grapes are irrigated by surface drip irrigation, considered to be an efficient means of watering compared to other contemporary methods. However, application of water to the soil surface contributes to water losses from both evaporation to the atmosphere and use by weeds. Surface drip irrigation also tends to concentrate the roots in the upper soil profile, which dries rapidly during summer temperatures, requiring frequent irrigation applications to maintain vine health (2). Subsurface irrigation has been shown to be more water efficient than surface applied drip irrigation (3, 4). Unfortunately, use of buried driplines to deliver the water subsurface have been plagued with problems of soil clogging and gopher damage (5).
Authors: Xiaochi Ma, Pete Jacoby and Jeremy Thompson, Crop and Soil Sciences, Washington State University, Pullman, WA
Poster presented at ASA, CSSA, SSSA Annual Meeting, Phoenix, AZ, 11/07/2016
Subsurface micro-irrigation, which delivers water directly into lower root-zone of grapevines, is considered a relatively new strategy to improve water use efficiency. However, buried driplines are subject to soil clogging and chewing damage by burrowing rodents. This presentation will illustrate an improved technique to avoid these issues and deliver drip irrigation at greater depths than buried lines. To better understand grapevine root response to deep irrigation (applied up to 1 m below ground), both greenhouse and field site experiments were initiated to investigate the impacts of subsurface micro-irrigation on grapevine growth and fruit production. Field work conducted in 2015 demonstrated that by using direct root-irrigation, grapevines could be sustained during extreme heat and drought conditions with only 15 percent the water applied as surface drip with full commercial rates. With the lowest rate (15 percent of commercial surface drip), grape production was 70 percent that of the full commercial rate, and with 60 percent of commercial surface drip application, fruit production was only 10 percent less that of commercial rates. Because this technique has shown ability to sustain grapevines at reduced water amounts from surface drip delivery, our research will determine impacts on the vine from two physiological aspects: carbohydrate partitioning and root dynamics. The mini-rhizotron method is employed to observe root architecture, turnover, and calculate biomass while photosynthetic rate is determined by auto-porometer. Results will not only help vineyard producers reduce irrigation water use while maintaining fruit production, but also lead to a better understanding of sustaining vine health during periods of sustained water shortages and drought stress.