Submitted to: World Congress of Soil Science
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2006
Publication Date: July 1, 2006
Citation: Alva, A.K. 2006. Set points for scheduling potato irrigation using capacitance probes. World Congress of Soil Science. On CD. Technical Abstract: Potato production in the US Pacific Northwest (PNW) is mostly on low organic matter sandy soils. The annual rainfall in some parts of this production region is <150 mm, thus, effective irrigation management is the key for sustainable production and net returns of Potatoes which is grown in 3 to 4 years rotation. The cumulative irrigation through center pivot systems (during May through August) in the Columbia basin production region varies from 720 – 800 mm. Potential leaching of nitrate below the rootzone is a concern. Improved N management practices combined with careful irrigation scheduling are necessary to increase crop water and nutrient uptake efficiencies and minimize N losses to groundwater. The tuber yield of optimal marketable quality is highly dependent on the adequate available soil water content during the growing season. Real time, continuous monitoring of soil water content within and below the root zone is necessary to fine tune irrigation scheduling to minimize the leaching loses below the root zone, while supplying adequate water for the plants to minimize the effects of water stress, which can have significant negative effects on the tuber production and quality. Capacitance probes were used in Potato fields to monitor the soil water content at 15, 30, 60, 90, and 120 cm depth. Depth integrated soil water content (0-60 cm depth soil. i.e. predominant root zone) corresponding to field capacity soil water content (Full point), 30 percent depletion of the available soil water content (Refill point), and at wilting point (Driest point) provided the set points for basing the irrigation. Our studies using Ranger Russet cultivar grown in a Quincy fine sand the Full point and Refill point were calculated as 72 and 54 mm for the top 60 cm depth soil, which represents the rooting depth for potatoes. The aim of irrigation management during the potato growing season should be to maintain the soil water content in the 0-60 cm depth between the Full point and the Refill point to minimize excess soil water content, which could leach below the root zone, and avoid soil water stress effects on the crop.