Measurements of light interception by navel orange orchard canopies: case study of Lindsay, California

Photosynthetically active radiation PAR intercepted by orange orchards Frost Nucellar navel having different canopy sizeswas measured to determine the relationships with crop coefficient Kco and Kcr values and crop evapotranspiration ET ETc. Threeseparate experiments were carried out near Lindsay, Calif. during the months of July and August 2004 to compute the fraction of lightPAR intercepted by mature and immature orange orchards. Periodic readings of PAR data were compared with near simultaneousmeasurements of net radiation Rn mV, heat transfer through exposed flux plates Fh mV, and incident total solar radiation Rs mV.The PAR data were used to calculate canopy light interception and the results were compared with those computed from the Fh and Rsdata. The other sensors were studied as possible substitutes for the more expensive PAR light bar. Light interception by the differentcanopies was related to crop coefficient Kco and Kcr values that were determined by micrometeorological measurement of ETc andPenman–Monteith reference evapotranspiration ETo and ETr.