Canopy Reflectance Estimates of Nitrogen Status in Arizona Cool Season Crops.

Active spectroradiometers have been successfully employed as indicators of N status and biomass in summer row crops such as cotton in the in the southwest US.  Durum wheat (Triticum durum L.) is a major cool season crop in the Sonoran desert of AZ, and there is growing interest in biofuel feedstock crops such as camelina (Camelina sativa L.)  and lesquerella (Lesquerella fendleri L.).  In the winter season of 2010-2011, we measured red (670 nm) and amber (590 nm) normalized vegetative difference vegetative index (NDVI) in replicated, N fertilizer rate studies in camelina, lesquerella and durum wheat.  Amber NDVI estimated in-season leaf N and N accumulation better than Red NDVI. Red NDVI correlated slightly better with biomass and yield compared to Amber NDVI.  Passive spectral data calibrated to white boards compared well with active sensor reflectance.