Critical Evaporative Demands for Differential Stomatal Action in Peanut Grown in Narrow and Wide Row Spacings1

Abstract

AbstractInduced stomatal closure behavior of irrigated peanut (Arachis hypogeaeL. cv. Comet, a bunch type) as related to row spacing and evaporative demand has been previously demonstrated as real and repeatable. The objective of this research was to determine the magnitude of evaporative demand that induced stomatal closure in narrow‐row plantings. Stomates in wide rows tended to show far less closure on the same days. The differences were not noted on days with low evaporative demand. Concurrent measurements of net radiation, dry‐ and wet‐bulb temperature, and horizontal wind velocity were made every 15 min. Estimates of environmental evaporative demand were made. No distinct peak or cumulative evaporative demand levels were found that separated stomatal differential action days from nonaction days. However, analysis of the cumulative advective energy component of cumulative evaporative demand showed a threshold above which stomatal closure responses were noted. This threshold was 8.5 MJ m−2. Further detailed analysis of the factors involved in the cumulative advective energy component indicated stomatal closure was dominated by neither horizontal wind velocity, integrated over time, nor integrated vapor pressure deficit.