Estimation of Rice LAI in a Large Scale Using Landsat Imageries

Leaf area index (LAI) is an important index in crop evapotranspiration estimation and in monitoring abiotic stresses like water stress. The LAI determination using direct methods is costly as well as time consuming¡ making it nearly impossible especially over large scales. For these reasons¡ attempts have been made to forecast LAI using remotely sensed vegetation indices (i.e.¡ the Normalized Difference Vegetation Index¡ NDVI). The present study aimed to estimate rice LAI in a large scale using remote sensing imageries from Landsat 5 and 7. Actual LAI were measured during 2010 in four different growing phases in 10 paddy fields of Fouman¡ Guilan¡ the northern part of Iran. The samples were taken from the fields and the LAI were measured by a LAI meter in laboratory. The results showed that the accuracy of estimation of LAI by Landsat imageries changed during the season¡ but the best results gained in rice full coverage in flowering phase (R2=0.85). In the early stage of rice growing season using NDVI and in full coverage using SAVI gave the best correlation of LAI estimation.