Monday, November 5, 2007
47-6
Feedback Control of Subsurface Drip Irrigation to Optimize Irrigation Research.
For competitive production of irrigated crops, growers need to optimize plant performance, often with reduced inputs to reduce off site effects of irrigation-induced erosion and irrigation-induced leaching. Yet irrigation research is often based on theoretical principles of crop evapotranspiration, water use efficiency, etc. with little focus on the ideal range of plant stress and the limits of the soil to retain water. The OSU team envisioned optimizing plant performance by keeping the soil in the optimal range of soil water potential for a given species (hence optimizing plant performance) and limiting the amount of water at each irrigation to the small amount that the upper 0.3 to 0.4 m of the soil surface could hold without leaching (hence minimizing off-site environmental effects of irrigation and minimizing water and fertilizer requirements). The environmental goals were needed due to groundwater and surface water contamination. These twin economic and environmental goals were accomplished by using measurements of soil water status as a signal for automated feedback control of irrigation. The experimental results have allowed closer determination of irrigation criteria than has been accomplished in the past and have laid the foundation for commercial drip irrigation of onion.
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