A possibility of an index of NDVI and SPAD to estimate protein contents of rice

Abstract

A new index combined with the normalized difference vegetation index (NDVI) and chlorophyll meter (SPAD) value is proposed and compared with the protein contents of rice grain, as the different time responses of NDVI and SPAD value were observed in the rice paddy measurements. The NDVI is determined from the spectrum measurement using spectrum radiometer. The SPAD value is measured by the chlorophyll meter of the soil and plant analyzer development (SPAD-502, Minolta). Time series of NDVI and SPAD value were measured at the paddy field in Atsushio, Fukushima prefecture, where the rice cv. Koshihikari is cultured with reduced agrichemical and organic fertilizer. The rice protein contents were determined by the taste analyzer, which analyses protein, amylose, and water contents of the rice grain. The variation index between NDVI and chlorophyll content (VNC index) was proposed with the time series measurements of two parameters from the ear emergence period to the duration grain filling. The VNC index and the protein content of rice grain exhibited a positive correlation. This study suggested a possibility to estimate the protein content of rice grain from the VNC index, where NDVI and SPAD value were combined.