Modelling light interception on the basis of sunfleck measurements | [Modélisation de l'interception de la lumière sur la base des taches de soleil]
1999
Wagenmakers, P.S. ((Fruit Research Station, Randwijk (Pays Bas))) | Tazelaar, M.
Canopy light interception is related to productivity and fruit quality. Therefore, optimum light interception is of strategic importance for growers. Up to 70 / diffuse light interception, the productivity of an apple or pear orchard increases without loss of quality. However, when more than 70 / of the incoming light is intercepted, the total production per ha may increase but the production of fruit quality will be affected negatively. Measuring light with PAR sensors under diffuse conditions is a reliable method but not always practical because such weather conditions do not always prevail. Measuring under direct light conditions is, however, more complicated since date, time and row direction influence the results strongly. Sunfleck estimations on the orchard floor have been related to direct PAR measurements and model calculations of light interception over a range of dates and time. The model input parameters were solar inclination and declination, and orchard characteristics such as tree shape and dimension, leaf area, planting system, and row direction. The visual rating of sunflecks on the ground was linearly correlated with direct light records. Therefore, a reliable estimation of orchard light interception on the basis of sunflecks seems possible, providing that latitude, date, time and row direction are taken into account
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