Relationships between Indexes Related to Vegetation Measured by Ground Sensing and Growth Traits in a Wheat Cultivar ‘Satonosora’.

Abstract

Relationships of six vegetation indexes to the aboveground biomass and nitrogen content at tillering and stem elongation stages were compared in a wheat cultivar ‘Satonosora’; normalized difference vegetation index (NDVI) measured with the portable crop growth sensor GreenSeeker, NDVI, green NDVI (GNDVI), simple ratio (SR) and chlorophyll index green(CI_green) measured with a spectroscope, and plant canopy coverage ratio (PCC) calculated from digital images. The aboveground biomass was highly related to PCC, followed by GNDVI and CI_green. These relationships were stronger than that to NDVI. The values of PCC, GNDVI and CI_green fitted with nitrogen content better than NDVI especially at the stem elongation stage. Unlike the other indexes, CI_green was not saturated even during the stem elongation stage, suggesting that it is suitable for estimating the nitrogen content at this stage. While PCC increased consistently throughout the survey period, the other vegetation indexes decreased temporarily under a dry soil condition at an early developmental stage. Therefore, for the indexes obtained with a spectroscope, an improved measurement method that is resistant to environmental fluctuation including soil moisture would better explain biomass and nitrogen content in wheat.