Evaluations of Intra-Field Variation of Soybean Growth with a Handheld NDVI Sensor

Abstract

The intra-field variation of soybean growth and its relations to the yield were evaluated using the normalized difference vegetation index (NDVI) measured with a handheld crop sensor ‘GreenSeeker’. NDVI of the soybean variety ‘Satonohohoemi’ cultivated in 2021 and 2022 was evaluated. In both years, the plots with a large number of seedlings per area showed high NDVI at the early growth stage. The plots with a high NDVI at the early growth stage indicated heavy aboveground dry weight at the flowering stage and at the early seed growth stage in both years. However, NDVI at the early growth stage was not related with yield in both years. At the late maturing stage, NDVI showed error values in the two plots among 30 plots because of early leaf withering. Although the yields of those two plots were not always low, the hundred-seed weights were clearly low. Those results suggest that NDVI at the early growth stage can be used to estimate the intra-field variations of soybean growth until the early seed growth stages to some extent and NDVA at the late growth stage can detect the poor maturing plots.