Relating X-band SAR Backscattering to Leaf Area Index of Rice in Different Phenological Phases

The objective of this study is to provide complete information on the dynamic relationship between X-band (3.11 cm) backscattering intensity (sigma degrees) and rice crop's leaf area index (LAI) at all growth phases. Though the relationship between X-band sigma degrees and LAI has been previously explored, details on the relationship at the reproductive phase remain unstudied. LAI at the reproductive phase is important particularly at the heading stage where LAI reaches its maximum as it is closely related to grain yield, and at flowering stage where the total leaf area affects the amount of photosynthates. Therefore, this study examined the relationship of increasing LAI (vegetative to reproductive phase) and decreasing LAI (ripening phase) with TerraSAR-X (TSX) ScanSAR (3.11 cm) sigma degrees at HH polarisation and 45 degrees incidence angle. The results showed a statistically significant (R-2 = 0.51, p value < 0.001) non-linear relationship of LAI with sigma degrees at the vegetative to reproductive phase while no significant linear relationship was found at the ripening phase. This study completes the response curve of X-band sigma degrees to LAI by filling in the information on the reproductive phase which more accurately characterises the dynamic relationship between the rice crop's LAI and X-band's sigma degrees. This contributes to improved knowledge on the use of X-band data for estimating LAI for the whole crop cycle which is essential for the modelling of crop growth and estimation of yield.