List of figures Fig. 1: Experimental design of cabinets. 6 Fig. 2: Measurement points of photosynthetically active radiation and air temperature. 10 Fig. 3: Time course of solar irradiation. Solar irradiation was mea sured every day and values for one week were cumulated. 12 Fig. 4: Photosynthetically active radiation (solar PAR + PAR of lamps) and air temperature at di fferent lighting regimes. PAR and air temperature was measured early in the morning at cloudy days. 13 Fig. 5: Soil temperature at different lighting regimes and different stem densities. The soil temperature was measured at little solar irradiation early in the morning. 14 Fig. 6: E.C. (a, c) and pH (b, d) of irrigation water (a, b) and runoff of irrigation water (c, d). 15 Fig. 7: Proportion of amount of runoff from applied irrigation water at different lighting regimes and stem densities. 16 Fig. 8: Water uptake at different lighting regimes and stem densities. 17 Fig. 9: Height of sweet pepper at different lighting regimes and stem densities. 18 Fig. 10: Relationship between height of sweet pepper and taken up water by sweet pepper plants at different lighting regimes and stem densities. 18 Fig. 11: Number of fruits (green and red) on the plant at different lighting regimes and stem densities. 19 Fig. 12: Cumulative total yield at different lighting regimes and stem densities. (1 st class: > 100 g, too little weight: < 100 g). 21 Fig. 13: Time course of accumula ted marketable yield at different lighting sources for interlighting and stem densities. 22 Fig. 14: Relationship between accumulated marketable yield and light intensity. 22 Fig. 15: Time course of accumula ted marketable yield at different lighting times and stem densities. 23 Fig. 16: Time course of accumula ted marketable yield at different lighting regimes and stem densities. 24 Fig. 17: Fruit set (fruit set (%) = (number of fruits harvested x 100) / total number of internodes) at different lighting regimes and stem densities. 25 Fig. 18: Sugar content of green and red fruits at different lighting regimes and stem densities. 27 III
Fig. 19: Dry substance of green (a) and red (b) fruits at different 28 lighting regimes and stem densities. 29 Fig. 20: N content of green (a) and red (b) fruits at different lighting regimes and stem densities. 30 Fig. 21: Dry matter yield of stripped leaves at different lighting regimes and stem densities. 31 Fig. 22: Cumulative dry matter yield at different lighting regimes and stem densities. 32 Fig. 23: Cumulative N uptake of sweet pepper (2 stems/plant). 33 Fig. 24: NO 3 N and NH 4 N in input and runoff water. 34 Fig. 25: NO 3 N and NH 4 N in pumice at the end of the experiment. 34 Fig. 26: Energy use efficiency in relation to lighting regimes and stem density. 39 Fig. 27: Revenues at different light sources and lighting times. 40 Fig. 28: Variable costs (without lighting and labour costs). 41 Fig. 29: Division of variable costs. 41 Fig. 30: Profit margin in relation to light sources and lighting times and stem density. 44 List of tables Tab. 1: Irrigation of sweet pepper. 7 Tab. 2: Average distance between internodes and number of inter nodes at different lighting regimes and stem densities. 20 Tab. 3: Cumulative total number of marketable fruits (red and green) at different lighting regimes and stem densities. 25 Tab. 4: Proportion of marketable a nd unmarketable yield at different lighting regimes and stem densities. 26 Tab. 5: Lighting hours, power and energy in the cabinets. 35 Tab. 6: Costs and costs for consumpt ion of energy for distribution and sale of energy. 37 Tab. 7: Variable costs of electricity in relation to yield. 38 Tab. 8: Profit margin of sweet pepper at different light sources and lighting times and stem densities (urban area, VA210). 42 IV