## 2 Experimental Design
### Instrumentation and Measurements  
Top of canopy spectral signatures were taken using the FieldSpec Pro 3 (Analytical Spectral Devices, Boulder, CO, USA) field portable spectrometer with a full spectral range located in the VIS, NIR and SWIR region (350-2,500 nm). Instrument sampling intervals (1.4 nm--VIS and NIR; 2 nm--SWIR) undergo an automatic internal interpolation to 1 nm spacing using linear and \begin{table}
\begin{tabular}{|c|c|c|c|c|} \hline \multicolumn{3}{|l|}{**Spring Barley**} \\  & & & beginning of & end of \\ seeding & first emergence & flowering & experiment & experiment \\ \hline \hline  & & & & \\ \hline March & April & May & June & July \\ \hline \hline seeding & first emergence & 4–6 leaves & beginning of & end of \\  & & unrolled & experiment & experiment \\ \hline \end{tabular}
\end{table} 
Table 2: Time schedule of the Bad Lauchstadt Experiment 2008. Black vertical pointers indicate in which part of the month particular events took place. polynomial equations [44]. All spectral surveys were taken under two conditions: First, reflectance was recorded from nadir position about 0.45-0.55 m above the top of the plant under sun illumination in the winter greenhouse with all walls and the roof removed. Second, two tungsten halogen quartz lamps: THQ (Dorr, Neu-Ulm, Germany) with 1,000 watt, 3,200 K color temperature, 26,000 Lumens of brightness each ([[http://www.doerrfoto.de/](http://www.doerrfoto.de/)]([http://www.doerrfoto.de/](http://www.doerrfoto.de/))) under closed room conditions were used. Both lamps were installed in a closed greenhouse room with walls covered with black mat paint. Lamps were pointed from two opposite directions and mounted at a 30\({}^{\circ}\) angle according to the floor plane. For reflectance scanning under THQ illumination, every sample pot had to be carried into the dark room using special lift truck designed to carry heavy load. Reference measurements were taken for both modes using a Spectralon (LabSphere, North Sutton, NH, USA) white reference panel (Effective Spectral Range: 250-2,500 nm, Reflectance within 400-1,500 nm: 99% and within 250-2,500 nm: more than 95%, Thermal Stability: up to 400 \({}^{\circ}\)C) at the beginning of each time series and after changes of sun illumination conditions under mode 1. Spectral data were collected throughout the experiment between 11:00 a.m. and 1:00 p.m. in order to avoid large impacts of bidirectional effects. Each reflectance spectra was calculated as an average over four individual spectral measurements (each averaged from 25 internal surveys) slightly varied around the pot center to avoid boundary effects per pot. LAI was measured using a LAI 2,000 plant canopy analyzer (LI-COR, NE, USA) directly after the spectral measurement under outside but shadowed conditions. Measurements were carried out considering individual calibration of the instrument in a way that the hemispherical field of view was least influenced by the experimental setup and conditions. Again, each data set was averaged over four individual measurements per pot. Soil moisture was measured as volumetric soil WC using a ThetaProbe ML2x FD-probe (Delta-T Devices Ltd, Cambridge, UK) for every sampling day. A probe length of 60 mm and a set of 4-10 measurements per pot (with regards to possible soil penetration dependent on soil softness/dryness) guaranteed an average water content in the upper root zone of the pot. In addition, vegetation height, and in case of sugar beet: leaves length, were monitored. The glasshouse experiment was started in the first week of June 2008 and was continued over a six weeks period until the second week of July. Measurements were taken at 15 individual dates however, as spectral reflectance measurements under outside conditions were limited due to unfavorable weather conditions, and as the reflectance spectra and derived SI's did not show any significant differences between both illumination conditions, we have limited our further analysis to the use of data obtained under indoor conditions.