Xiaochi Ma, Pete Jacoby and Jeremy Thompson, Crop and Soil Sciences, Washington State University, Pullman, WA
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.