Radiometric estimation of biomass and nitrogen content of Alicia grass

Abstract Hand-held MARK-II radiometric measurements were used to estimate biomass yields and nitrogen (N) content of Alicia grass (Cynodon spp.) plots having five levels of nitrogen fertilization. The radiometric RED (630- to 690-nm) and NIR (760- to 900-nm) measurements obtained from the plots were converted to reflectance factors and to perpendicular (PVI) and ratio (RVI = NIR/RED) vegetation indices and then correlated with grass biomass yield and N content. The coefficients of determination (r2) in estimating biomass yield for the RED and NIR reflectance factors were 0.04 and 0.73, 1 respectively, and for PVI and RVI they were 0.68 1 and 0.61, 1 respectively. The correlations for N content were 0.02, 0.71, 1 0.69, 1 and 0.60, 1 respectively. Since beef cattle protein needs are related to grass N content these results may be useful to operational rangeland remote sensing programs for estimating animal carrying capacity using satellite data.