Feasibility of using pyranometers for continuous estimation of ground cover fraction in table grape vineyards
Antonio Martinez-Cob | Jose M. Faci | Olga Blanco | Eva T. Medina | Kosana Suvočarev
<p class="Abstract">This paper evaluates the feasibility of using pyranometers for continuous estimation of ground cover fraction (GCF) at remote, unattended sites. Photographical techniques were used for measuring GCF (GCF<sub>ref</sub>) at a table grape vineyard grown under a net. Daily pyranometer-driven GCF estimates (GCF<sub>pyr</sub>) were obtained from solar radiation measurements above and below the canopy. For GCF<sub>pyr</sub> computation, solar radiation was averaged for two hours around solar noon (midday periods) and for daylight periods (8:00 to 18:00 Universal Time Coordinated). GCF<sub>pyr</sub> and GCF<sub>ref</sub> (daylight periods) showed a good agreement: mean estimation error, 0.000; root mean square error, 0.113; index of agreement, 0.967. The high GCF attained, the large measurement range for GCF and the presence of the net above the table grape were the likely reasons for the good performance of GCF<sub>pyr</sub> in this crop despite the short number of pyranometers used. Further research is required to develop more appropriate calibration equations of GCF<sub>pyr</sub> and for a more detailed evaluation of using a short number of pyranometers to estimate GCF.</p>
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