Remote sensing-based biomass maps for an efficient use of fertilizers

For decades the main objective of farmers was to get the highest yields from their farmland. Nowadays, quality of agricultural products is becoming more and more important for the largest returns. Particularly a homogeneous quality is often required for getting highest product prizes. In addition to the agricultural products themselves, the effects on our environment are becoming more and more important. These put increasing limitations on modern agriculture. Therefore, site specific management of individual parcels is a hot topic in agriculture all over the world. One of the tools to make site specific management possible is the use of biomass maps showing the variability within a parcel as a result of differences in growing conditions. Based on a biomass map a farmer can take site specific actions to improve his overall management within a parcel. Within this study biomass maps were made of a potato parcel based on false-colour aerial photographs. The LORIS® service was used to convert the photographs into georeferenced relative biomass maps. In this experiment it was assumed that nitrogen nutrition is the main factor the farmer can influence to change the yield distribution within the potato parcel. Field trials were set up with different nitrogen levels to test whether the concept of site specific management works and to study how big the effect is. Spectrometer measurements in the field were used to study the evolution of biomass during the growing season and to test the effects of the fertilization levels. Results show on the one hand the merit of biomass maps derived from remote sensing for improving the product quality within a parcel and on the other hand how spectroscopic measurements obtained during the growing season can help in explaining the yield differences found at harvest time. In particular the so-called red-edge index was very valuable for monitoring growth differences in potatoes.