## 2 Experimental Design  
### Study Site and Experimental Setup  
Experimental data have been obtained during the growing season 2008 at the field research station of the UFZ-Helmholtz Centre for Environmental Research in Bad Lauchstadt (BL), Saxony-Anhalt, Germany (51\({}^{\circ}\)23'32\({}^{\prime}\)N 11\({}^{\circ}\)52'33\"E, altitude 113 m a.s.l., mean annual precipitation 484 mm, mean annual temperature 8.7 \({}^{\circ}\)C; [41]). Two main German agricultural crop species, spring barley (_Hordeum vulgare L._) and sugar beet (_Beta vulgaris ssp._), were chosen as objects of investigation. A total of 24 pots were planted using black soil in circular-shaped pots, 0.6 m in diameter and 0.8 m high, 12 for spring barley and 12 for sugar beet. There were four sugar beet plants per pot and spring barley was planted in rows, allowing five rows per pot separated by 0.125 m as illustrated in Figure 1.  
Selected crops were seeded and grown in the winter greenhouse equipped with removable walls and roof that were left open during the day and closed during the night and rainfall events. This allowed plant growth under most possible natural environment conditions while being able to examine crop response to artificially produced water stress under different nutrient conditions. After seeding at the  
Figure 1: Schematic **(a)** and example pots for sugar beet **(b)** and barley **(c)** (18.06.2008).  
beginning/mid of April, all pots were initially cultivated under normal, well watered conditions (defined by 60% of soil field capacity that has been derived from 24 h capillary saturation of 100 cm\({}^{3}\) soil cores, and 2 h ex-filtration on a 6 cm sandbed). The spectral and other measurements under controlled conditions started in the first week of June when soil/plot covering by plants was almost complete. Spring barley was in the flowering stage roughly 6-7 weeks after first emergence. For sugar beet the measurements started when 4-6 leaves were unrolled and fully developed. Table 2 gives a detailed overview about phenological stages and the time schedule of the experiment.  
At the start of the experiment, pots were treated with different water and nutrient conditions. Two variants concerning nutrient treatment and three different modes of irrigation were considered. The Bad Lauchstadt soil used in this experiment is _Haplic Chernozem_ (FAO classification) developed from loess [42] with 22% clay [41] characterized by a very high organic carbon (C\({}_{\mathrm{org}}=19.8\) g kg\({}^{-1}\)) and total nitrogen (N\({}_{\mathrm{tot}}=1.6\) g kg\({}^{-1}\)) contents [43]. Before seeding, all sample- pots were filled with 150 kg of soil material, 12 pots (six for sugar beet and six for spring barley) received an addition of mineral fertilizer, while the other 12 pots were kept as a reference without fertilizer. The amount of mineral fertilizer applied was defined in accordance with the \"Standard Bad Lauchstadt\" treatment praxis (15 g P and N as well as 20 g K per pot). The two fertilizer treatments are called \"N-low\" or \"N-high\" in the following. Three different water treatments have been applied defined as follows: a \"high\" WC was defined by controlling WC at a value of 60% of the soil field capacity, for a \"medium\" variant this value was set to 30% of field capacity, and \"low\" variant was defined by no additional water supply. The water status/content was verified every second-third day by weighting of the pots, followed by an irrigation to compensate for the evapotranspiration losses. In total, 24 pots including two different crop species under two nutrient and three irrigation treatments are considered and investigated, and each combination has two replicates.