Research on detection of rice ecotypes by canopy spectral reflectance

From the view point of food security, observation of crop growth and estimation of crop production is eagerly required. Although satellite observations based on remote sensing have already been conducted, improvement on estimation accuracy is still necessary. One of the possible ways is combination of remote sensing with crop growth simulation model. However, simulating results quite varied by parameters which were mostly determined by cultivar ecotypes. Accordingly, detection of rice ecotypes is probably quite informative and improves the estimating accuracy. This study preliminarily conducted research on detection of cultivar ecotypes by canopy spectral reflectance on the ground level for rice which is the major crop in Asia. We conducted field experiments in Kyoto in 2011 and 2012, with 8 cultivars (3 japonica and 5 indica cultivars) including traditional and improved types, and indica and japonica types. Canopy multispectral reflectance of rice canopies was measured once a week by MS-720 (Eko Instruments) from 1m above canopy. Cluster analysis showed that canopy multispectral reflectance was significantly different between cultivars. The difference depends on a form of plants and height and the result may enable us to distinct rice cultivars in plant communities. Our previous study proposed a new indicator (TIPS: Time-series change Index of Plant Structure) for leaf area index (Hashimoto et al., 2009). Common vegetation indices such as NDVI are thought to indicate canopy coverage, suggesting that the difference between TIPS and vegetation index contributes to detect cultivar ecotypes in rice.