Note: Program subject to change without notice

Wednesday, November 7, 2007
306-2

Soil Water in Relation to Irrigation, Uptake, and Potato Yield in a Humid Climate.

Gordon Starr1, Diane Rowland2, Timothy Griffin1, and O.M. Olanya3. (1) USDA-ARS, 38 Fountain Street, Bangor, ME 04401, (2) USDA-NRCS, USDA-ARS Nat'l Peanut Research Lab, PO Box 509 1011 Forrester Dr. Se, Dawson, GA 39842-0509, (3) NEPSWL, USDA-ARS, University of Maine, Orono, ME 04469

Efficiently controlling soil water content with irrigation is essential for water conservation and often improves potato yield. Volumetric soil water content (Θv) in relation to irrigation, plant uptake, and yield in potato hills and replicated plots was studied to evaluate four water management options. Measurements of Θv using a hammer driven probe were used to derive a Θv index representing the relative Θv status of replicated plots positioned along a hill slope. Time series for Θv were determined using time domain reflectometry (TDR) probes at 5 and 15 cm depths at the center, shoulder, and furrow locations in potato hills. Sap flow was determined using flow collars in replicated field plots for four treatments: un-irrigated, sprinkler, surface drip, and sub-surface drip irrigation (40 cm burial). Irrigated yields were high/low as the Θv index was low/high suggesting Θv excess was a production problem in the wetter portions of the study area. The diurnal pattern of sap flow was reflected in the Θv fluctuation it induces at hill locations with appreciable uptake. Hill locations with higher plant uptake were drier as was the case for the 5 cm (dry) depth relative to the 15 cm (wet) and the locations in the hill (dry) relative to the furrow (wet). The surface drip system had the lowest water use requirement because it delivers water directly to the hill locations where uptake is greatest. The subsurface drip system wetted the hill very gradually (1-2 days). Measurement of the Θv index prior to experimental establishment could improve future experimental design for treatment comparisons.