Estimating Stem Water Flow in Peanut (Arachis hypogaea L.) Under Different Irrigation Methods

Abstract

The ability to measure plant water use directly could address a myriad of problems in peanut production from irrigation scheduling to aflatoxin management. One of the most effective methods of measuring plant water use is via the sap flow method; however this technique has not been tested in peanut in a field setting. In this study, sap flow collars were installed on peanut plants growing under overhead irrigation (OH), subsurface drip irrigation (SDI), and non-irrigated (NI) production. Using this experimental set-up the following objectives were addressed: 1) determine if the technique of sap flow measurement could be successfully utilized in peanut; 2) determine if daily peanut stem water flow, biomass partitioning, and carbon isotope discrimination differed among irrigation treatments, and 3) determine what environmental parameters were most closely correlated with peanut stem water flow. Peanut stem water flow was successfully measured during a two week period coinciding with active pod fill. Mean daily flow rates ranged from 4–6 g/ hr in irrigated treatments and from 1–2 g/hr in the dryland treatment. Significant differences among irrigation treatments existed in daily water use patterns, average daily water use, and cumulative daily water use based on plant sap flow. Soil moisture, soil temperature, and canopy surface temperature were significantly correlated with plant sap flow. Significant differences also existed among irrigation treatments in plant size with SDI plants having more leaf mass, longer internodes, and overall larger canopies than either the OH or NI plants. Even though SDI plants had much greater aboveground biomass than plants in the other treatments, yields did not differ between irrigation methods indicating SDI plants may have had lower water-use efficiencies than either OH or NI plants. However, seasonal water-use efficiency measurements represented by carbon isotope discrimination results did not definitively show this. This study has shown the efficacy of sap flow measurement in peanut and the potential applications of this technique in future irrigation studies.