Department of Plant Sciences

Traditional vegetation indices like normalized difference vegetation index (NDVI) tend to saturate under high canopy coverage conditions and do not perform very well for diagnosing nitrogen status of high yielding crops. Red edge indices have been shown to be more sensitive to nitrogen status and are promising alternatives. The objective of this study is to evaluate different red edge indices for estimating winter wheat (Triticum aestivum L.) nitrogen status under high canopy coverage conditions in farmers’ fields. Six 200 × 200 m fields in four villages from Shandong Province, China were selected for this research from 2005 to 2007. Hyperspectral reflectance was determined at Feekes growth stage 7-9 when wheat canopy was fully covered. Subsequently, linear relationships between red edge indices and plant N uptake and concentration were established. Results indicated that red edge position indices REP and REIP performed better in estimating plant N status than normalized and simple ratio red edge indices. Plant N uptake, as a better indicator of crop N status, was easier to estimate using red edge indices than plant N concentration.