PARENT SESSION
Poster Session 1: Photosynthesis and Water Relations
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Evaluation of water infiltration and use in peanuts with a ²H, soil water content, and root distribution model.

Leffler, A. Joshua^*,1, Rowland, Diane², ¹ Louisiana Tech University, Ruston, Louisiana² United States Department of Agriculture, Dawson, Georgia

ABSTRACT- The two-layer model of water use by plants compartmentalizes plant water sources into "near-surface soils" and "deep soils". Although this division has lead to many important findings in plant/soil water relations, it fails to recognize the continuum of soil resources available to plants with increasing depth. Use of water from soils at different depths is dependent on soil water content, root distribution, and plant demand for water. We develop a model to incorporate these parameters with a ²H label of soil water to examine infiltration and water use in peanut plants following a simulated precipitation event. We applied a ²H label to experimental plots of peanuts containing two cultivars (Georgia Green and Andru II) under two irrigation regimes (overhead sprinkler and sub-surface drip). Soils at four depth increments (10, 20, 30, and 40 cm) below the surface and stem tissue were sampled prior to addition of the ²H label and for three days after the simulated precipitation. Root distribution was determined with mini-rhizotron tubes and a camera system installed in the experimental plots. Of the 8.5 mm of experimental precipitation, ca. 4 mm infiltrated into the soil; 3 mm were retained in the uppermost 10 cm, and ²H data indicate a small amount infiltrated below 20 cm, although this may only be the case in plots receiving drip irrigation. We observed a linear decline in root length with depth. Overall, plants obtained nearly 40% of their water from the uppermost 10 cm one day following precipitation; water use from the uppermost 10 cm declined to 25% and 21% two and three days following precipitation, respectively. One day following precipitation, Georgia Green obtained ca. 45% of its water from the uppermost 10 cm while Andru II obtained only 29% from the same depth; water use among soil layers was similar for both cultivars on subsequent days. These data are also used to construct and evaluate a four-layer model of water use by peanut plants.

Key words: water use, root distribution, irrigation, Arachis