Common bean (Phaseolus vulgaris L.) is extensively grown in production zones where water is limiting. Crop water use efficiency is the ratio of biomass or seed yield produced per unit of water evapotranspired in a particular environment. Transpiration effi ciency (TE) is the ratio of yield per unit of water transpired. Th e objectives of this study were to: (i) determine the water use effi ciency (WUE) for six common bean genotypes (BAT 477, Morales, SEN 3, SEN 21, SER 16, and SER 21) in the greenhouse and for two genotypes in the fi eld (Morales and SER 16) and (ii) determine TE for two common bean genotypes using estimated evapotranspiration rates in the fi eld. Th ree greenhouse trials and two fi eld trials were conducted during 3 yr in Puerto Rico. Th ree water levels in the greenhouse and two in the fi eld were applied. Actual evapotranspiration was estimated using the generalized Penman-Monteith model based on aerodynamic and surface resistance, and with drainage type lysimeters in the fi eld. Diff erences among genotypes for WUE were found in the greenhouse experiments, with SEN 3 and SER 21 showing superior WUE in several treatments. In the fi eld, TE and WUE were aff ected by water level, and TE was consistent with previously reported coeffi cients for common bean.

<p>La zona cafetera colombiana está ubicada enteramente en el hemisferio norte, entre los 1 y 11° grados de latitud, sobre la cordillera de los Andes. Esta condición (ecuatorial andina) ha hecho que se dé por sentado que la variación temporal de la temperatura es mínima y que por ello, en su mayor parte la variabilidad de este elemento es espacial, atribuible casi exclusivamente a los cambios en altura sobre el nivel del mar. En este estudio se exploran factores de variación alternas, que muestran cómo, además de la altitud, otros factores, como la latitud, la zona de convergencia intertropical, El Niño Oscilación del Sur y el Cambio Climático, inciden sobre esta variable climática, que a su vez ejerce un papel fundamental sobre las plantaciones de cafeto.</p>

This paper presents the conceptualization, methodological adjustment and experimental application of the micrometeorological technique eddy covariance - EC, to measure energy, water vapor and CO2 fluxes in two coffee agroecosystems: the first under full sunlight, and the second under shade, both with equatorial Andean hillslope conditions. With a footprint and fetch calculation, the required distance from the edge of the field in the prevailing wind direction to the EC tower is three times higher under shade than full sun. The shaded agroecosystem reached maximum average carbon fixation rates of 21.26 ± 2.469 μmolCO2.m-2s-1 ( = 0.05) (61% higher than under 100% sunlight) which gives a high carbon sink capacity to the association of coffee plants with shading Pigeon peas (Cajanus cajan L). The average evapotranspiration rate was 2.33 ± 0.0102 mm.d-1 ( = 0.05) and 2.08 ± 0.00732 mm.d-1 under shade and 100% sunlight, respectively. The proportion of net radiation that reached the soil was 2% under shade and 4% under 100% sunlight. Likewise, the soil energy loss during the night was lower under shade, indicating less day-night temperature range in the latter agroecosystem. The methodological adjustment and the results of this first work using EC in Colombian coffee plantations, contribute to the development of reliable research regarding gas and energy exchanges between the atmosphere and ecosystems in conditions of the equatorial Andean hillslope.

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