NDVI measurements as a predictor of Miscanthus × giganteus biomass

Miscanthus × giganteus is important to biofuel production. Normalized difference vegetation index (NDVI) is useful in estimating vegetative biomass. The research objectives were to evaluate NDVI measurements, and their timing, as estimates of Miscanthus biomass and yield at harvest. Miscanthus was grown from 2010 through 2014 at five residual soil fertility levels resulting from annual applications of 0, 2.2, 4.5, 9.0, and 18.0 mg manure/ha from 2000 to 2005. The manure rates were laid out in a completely randomized design with eight replications. In 2014, a handheld Greenseeker™ (NTech Industries) sensor was used to determine NDVI from May 16 to June 25. Plant height was used as a proxy for biomass. Soil organic matter (SOM) and a suite of soil chemical properties related to soil fertility were determined. In 2014, SOM ranged from 27.9 to 47.1 g SOM/kg soil. Plant height/biomass differences due to residual fertility increased with time; taller plants resulted in greater NDVI values. Soil fertility did not affect NDVI prediction efficiency for Miscanthus height/biomass. Using a quadratic-plateau equation, NDVI data achieved saturation in late June, indicating that, from both practical (greatest spread in NDVI values) and statistical perspectives, early June was the best time to measure NDVI for yield prediction purposes.