Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 22, 2003
Publication Date: November 3, 2003
Citation: STOCKLE, C., KEMANIAN, A., HUGGINS, D.R., HOWELL, T.A. 2003. TRANSPIRATION-DRIVEN MODELS FOR CROP GROWTH SIMULATION. ANNUAL MEETING ABSTRACTS 2003. ASA-CSSA-SSSA, DENVER, CO. 2003 CDROM. Technical Abstract: The daily potential growth of crops depends on the availability of radiation and water for transpiration. Transpiration driven simulation models compute growth from an estimate of daily transpiration obtained from an independent subroutine that determines the evaporative demand of the atmosphere and the capability of the soil-crop system to supply that demand based on soil water content, canopy cover and rooting depth and distribution. However, the transpiration efficiency (TE, dry matter produced per unit mass of water transpired) is also a function of the evaporative demand. In this work, we discuss two strategies to calculate TE: (1) TE = kd/D, and (2) TE = ke/EToc where kd and ke are crop dependent constants, D is the daytime air vapor pressure deficit, and ETo is the reference evapotranspiration. Daily data of transpiration of barley and wheat at Pullman, WA, and data of wheat, corn and sorghum taken at Bushland, TX, were normalized by either D or ETo and regressed vs. the cumulative biomass to obtain kd and ke. Preliminary results obtained at Pullman indicate kd values of about 6 Pa, and ke values of about 25 g/m2 for both barley and wheat. Since D and ETo are highly correlated, we expect that both represent appropriate conversion coefficients. However, the ETo-based TE could have advantages in days of low D and high wind speed, where the use of D-based TE could overestimate the daily growth.