The effects of elevated carbon dioxide, temperature and soil moisture on the water use of stands of groundnut (<i>Arachis hypogaea</i>L.)

Abstract

Stands of groundnut (Arachis hypogaea L. cv. Kadiri 3) were grown in controlled environment glasshouses at two mean air temperatures (28 °C and 32 °C), two atmospheric CO2 concentrations (375 ppmv and 700 ppmv) and two soil moisture treatments (irrigated weekly to field capacity or allowed to dry from 22 d after sowing). The transpiration equivalent, Ωw (g kPa kg−1) the product of the accumulated bio-mass/transpired water ratio and the saturation deficit—was calculated for all the treatments using above-ground harvest, root core and neutron probe measurements. Neither temperature nor soil moisture treatment was found to have an effect on Ωw Increased CO2 concentration raised Ωw from 6.21 ±0.30 to 7.67 ±0.29 g kPa kg−1, an increase of 24%(P<0.005). The importance of accounting for root material and pod composition when calculating Ωw was highlighted.