Estimating Wheat Yield with Normalized Difference Vegetation Index and Fractional Green Canopy Cover

Abstract

Core Ideas Normalized difference vegetation index and fractional green canopy cover best estimated wheat grain yield. Normalized difference vegetation index and fractional green canopy cover measurements should be conducted prior to Feekes 6 growth stage. Camera height should be adjusted to capture three rows of wheat in the image when using fractional green canopy cover to estimate wheat grain yield. Producers are interested in methods for estimating wheat grain yield at earlier growth stages. Ability to estimate wheat yield early in the growing season could provide producers with the flexibility needed to decide whether to terminate their wheat crop to plant a more profitable alternative crop, such as soybean. The traditional assessment method, counting plants and tillers, is tedious and time consuming. There is a need to create easier methods to estimate wheat yield, such as normalized difference vegetative index (NDVI) or fractional green canopy cover (FGCC). The objective of this study was to compare NDVI, FGCC, and stem count measurements at multiple wheat growth stages to estimate winter wheat grain yield. Trials were established during the 2015–2016 and 2016–2017 growing seasons at two locations in Ohio. Treatment included wheat seeding rates of 0.75, 1.0, 1.5, 2.0, and 2.5 million seeds/acre to mimic a poor to excellent wheat stand. Wheat stand assessment methods of NDVI, FGCC, and stem counts were conducted at Feekes 1 (emergence), Feekes 5 (leaf sheaths strongly erect), and Feekes 6 (first node visible) growth stages. Regression models were used to estimate wheat yield. Normalized difference vegetation index (R2 = 0.49) and FGCC (R2 = 0.45) best estimated wheat grain yield while stem count measurements accounted for 29% of the variability in yield. However, NDVI and FGCC measurements are time sensitive and should be conducted prior to Feekes 6 growth stage, and for FGCC, camera height should be adjusted to capture three rows of wheat in the image.