To describe spatial heterogeneity of crop properties, non-destructive methods can be helpful in capturing whole field data sets. This paper shows examples of different sensor methods that have been evaluated to measure biomass and legume content in legume-grass mixtures. Biomass has been estimated using vegetation indices (NDVI, SR, EVI and REIP) calculated from spectral reflectance measurements in greenhouse experiments. The index REIP has been used to identify species composition as well. Furthermore, biomass values can be derived from ultra sonic measurements of sward heights. To quantify legume contents in short term leys, which is important for forage quality and nitrogen flows, image analysis tools have been used in different experi-ments with good results. These examples indicate a hopeful perspective to estimate biomass and species composition. However, the structural and functional complexity of legume-grass mixtures requires adapted methods to specific crop characteristics like e.g. predefinition of legume species
