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Accueil | Français » Publications » DEA et Masters » Contribution à l’amélioration de la mesure du Lai sur le mil(Pennisetum (...)

Contribution à l’amélioration de la mesure du Lai sur le mil(Pennisetum glaucum (L.) R. Br.) par utilisation du Lai-2000

Mémoire de fin d’études soutenu par M. Amadou SOUMANA le 25 Août 2010 à l’UCAD, Département de Biologie Végétale


In recent years several works have been conducted in CERAAS to improve the forecasting model SARRA_H. Several methods of leaf area index determination have been studied. A recent study on millet showed that LAI-2000 underestimate importantly the LAI value compared to those obtained by destructive method with planimeter, when the LAI measured exceed 2 (m²/m²). The overall objective of this study is to improve the determination of LAI with the LAI-2000, and it aims at first (i) to check the device LAI-2000 which has been used in the previous works and (ii) to verify if it is conform to use 90° angle to measure millet LAI even for high values ; then (iii) to analyze the possible effects of various factors such as time of measurement, seedling rate and cultivar on LAI-2000 measures and at last (iv) to seek algorithms of correcting the LAI-2000 measures. Analyses were focused on existing data and other collected on an experiment conducted during the rainy season 2009. All data have been established by measurements made in pairs with the LAI-2000 and the planimeter. The LAI-2000 tested provides similar values to those of a second device recently calibrated by the manufacturer (Licor). The LAI values obtained with the 90° and 180° views angle are identical and greeter than values obtained with the 360° angle, a result which proves that there was no on particular bias to measure high values of millet LAI with 90° view angle. Moreover, the time of measurement (morning or evening) has no significant effect on LAI-2000 measures. In additional, the study shows that the seedling rate and the variety used do not affect the precision of LAI-2000 measures. We observed a sensitivity of the LAI-2000 estimates to the presence of ears whose effect can reach 20% of the LAI measured from 50% ears emergence rate. We have found empirically a coefficient equal to 0,8 which permits to correct ears effect. After that a general polynomial equation of correcting LAI-2000 measures has been adjust, and has shown by checking a satisfactory level of correction. However, it efficiency is less from beginning to after flowering, that could be due to the effect of certain factors (senescence, candles ...) which are present in advanced stages of millet development.
Key words : Leaf area index “LAI”, LAI-2000, planimeter, millet.