Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2003
Publication Date: 11/1/2003
Citation: Kemanian, A., Stockle, C., Huggins, D.R., Kiniry, J.R. 2003. Regional scale variations of radiation - use efficiency in response to the environment [abstract]. Agronomy Abstracts. Paper no. A03-stockle537550-oral.
Technical Abstract: The conversion of crop intercepted radiation to biomass is usually referred to as radiation-use efficiency (e). The constancy of e is the basis of growth calculation in many crop models. In this work we show that e of non-stressed barley and wheat crops varies within the growing season and across regions mainly driven by the vapor pressure deficit of the air (D), likely an expression of atmospheric evaporative demand. Values of e for wheat and barley were gathered from the literature. In addition, a field experiment was conducted at Pullman, WA including two cultivars of spring barley (Baronesse and (Steptoe) seeded at two densities and two sowing dates in the years 2000 and 2001. Treatments were arranged in completely randomized blocks with four (2000) or three (2001) replications. Crops were fully irrigated. Growth was monitored through weekly sampling and intercepted solar radiation was measured continuously. Barley e was computed as the slope of the relationship between cumulative biomass and intercepted radiation. The maximum e of barley was 1.23 g MJ-1, which is below the maximum reported for wheat (1.5 to 1.6 g MJ-1). However, when the e of both barley and wheat were regressed against D both species fell on the same linear regression (intercept = 1.85 g MJ-1, slope -0.52 g MJ-1 kPa-1, r2 = 0.82, n = 21). This work suggests that maximum e should be adjusted by D; ignoring this effect could lead to gross overestimations of biomass production in arid environments.