000K utf8 1100 $c2022 1500 eng 2050 urn:nbn:de:gbv:8:3-2023-00609-0 2051 10.3390/rs14184525 3000 Holzhauser, Katja 3010 Kage, Henning 3010 Kühling, Insa 3010 Räbiger, Thomas 3010 Rose, Till 4000 Estimation of Biomass and N Uptake in Different Winter Cover Crops from UAV-Based Multispectral Canopy Reflectance Data [Holzhauser, Katja] 4209 Cover crops are known to provide beneficial effects to agricultural systems such as a reduction in nitrate leaching, erosion control, and an increase in soil organic matter. The monitoring of cover crops’ growth (e.g., green area index (GAI), nitrogen (N) uptake, or dry matter (DM)) using remote sensing techniques allows us to identify the physiological processes involved and to optimise management decisions. Based on the data of a two-year trial (2018, 2019) in Kiel, Northern Germany, the multispectral sensor Sequoia (Parrot) was calibrated to the selected parameters of the winter cover crops oilseed radish, saia oat, spring vetch, and winter rye as sole cover crops and combined in mixtures. Two simple ratios (SRred, SRred edge) and two normalised difference indices (NDred, NDred edge) were calculated and tested for their predicting power. Furthermore, the advantage of the species/mixture–individual compared to the universal models was analysed. SRred best predicted GAI, DM, and N uptake (R2: 0.60, 0.53, 0.45, respectively) in a universal model approach. The canopy parameters of saia oat and spring vetch were estimated by species–individual models, achieving a higher R2 than with the universal model. Comparing mixture–individual models to the universal model revealed low relative error differences below 3%. The findings of the current study serve as a tool for the rapid and inexpensive estimation of cover crops’ canopy parameters that determine environmental services. 4950 https://doi.org/10.3390/rs14184525$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:gbv:8:3-2023-00609-0$xR$3Volltext$534 4961 https://macau.uni-kiel.de/receive/macau_mods_00003932 5051 333.7 5550 catch crops 5550 NDV 5550 Parrot Sequoia 5550 pure and mixed canopies 5550 remote sensing 5550 sensor calibration