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Title: Importance of Real-Time, Continuous Monitoring of Soil Profile Water Content to Improve Potato Irrigation

Author
item Alva, Ashok
item MOORE, AMBER - University Of Idaho

Submitted to: International Symposium on Soil Water Measurement Using Capacitance Impedance and Time Domain Transmission
Publication Type: Proceedings
Publication Acceptance Date: 2/25/2009
Publication Date: 4/7/2010
Citation: Alva, A.K., Moore, A.D. 2010. Importance of Real-Time, Continuous Monitoring of Soil Profile Water Content to Improve Potato Irrigation. International Symposium on Soil Water Measurement Using Capacitance Impedance and Time Domain Transmission.

Interpretive Summary:

Technical Abstract: Center pivot irrigation is predominant in this region with irrigation often to replenish full evapotranspiration (ET). Optimal irrigation management is critical for sustainable production of high quality potatoes in the U.S. Pacific Northwest (PNW). During most years, the annual cumulative irrigation for potato is about 800 mm. This amount of total irrigation may be excessive; however, investigations on suitability of deficit irrigation have not been conclusive. Real-time monitoring of soil water content in the soil profile within and below the rootzone is important for evaluation of different irrigation systems to ensure that adequate soil water content is maintained within the rootzone to avoid potential negative effects of water stress on plant growth and production. Likewise, monitoring of soil water content below the rootzone provides evidence of water leaching into this zone which decreases water uptake efficiency and contributes to leaching of nutrients and chemicals from the rootzone. This study was conducted in a sandy Entisol (sand content >95% in the top 120 cm depth), using ‘Ranger Russet’ cultivar. Irrigation scheduling to replenish full ET or 70% ET (deficit irrigation) was evaluated. Soil water content was measured on real-time using Enviroscan capacitance probes installed at 10, 30, 60, 90, and 120 cm depths. The first three depths represent the rootzone. Irrigation to replenish full ET revealed that depth integrated water content in the top 60 cm soil (rootzone) was mostly above the “Full Point” during most of the growing season, this indicated potential leaching of water below the rootzone. While the deficit irrigation maintained water content in the rootzone between “Full Point” and “Refill Point”, with few exceptions in June only. Therefore, assuming our setpoints are accurate, this study indicates that irrigation to replenish ET may be leading to some degree of leaching losses below the rootzone. However, a thorough long-term investigation on the tuber yield and growth response to deficit irrigation is needed to support recommendations on fine-tuning irrigation scheduling.