Water deficit in common beans. II. Energy balance

Abstract

Energy balance components were evaluated in 1983, in a common beans (Phaseolus vulgaris L.) crop subjected to varying conditions of soil water availability and atmospheric evaporative demand, in a field experiment conducted at Piracicaba, SP, Brazil, at 22^o43'33" south latitude, 47^o38'00" W longitude, and 576 m altitude. The crop was sown in three dates (July 7, July 22 and August 4), each one submitted to two levels of soil water availability: with continuated irrigation and with a period of water stress caused by a 18-day period without rain fall (Sept. 25 to Oct. 12). The amounts of energy used in evapotranspiration increased with leaf area index, soil water availability, and atmospheric evaporative demand; the contrary occurred with the fractions of radiation used in air and soil heating. Reference evapotranspiration by Penman method (ETp) and evaporation from "class A" pan (ECA) were highly correlated with the flux of latent heat of evaporation (LE) calculated by the energy balance method. In plots with irrigation and high leaf area index, ETp appeared to estimate with high approximation LE, whereas unadjusted ECA overestimated LE.