2.3.2. Evaluation and Light Optimization

During the simulations based on the found response function, *Lmin* and the growth parameters *t<sup>e</sup>* and *t<sup>m</sup>* were set according to the treatment B310 (baseline scenario). The simulated height until the third internode fitted well with the measurement at the last day, which was also used for parameterization of the model. This shows that the response function was well integrated in the model. Comparing to earlier measurement days which were not used for parameterization of the model, the simulations had a tendency of underestimating the height under low BPFD levels (B60–B110). Importantly for the alternative scenarios the simulated height until third internode fitted well under the higher BPFD levels (B160–B310) (Figure 4).

**Figure 4.** Simulated (line) and measured (points) plant height until the third node and root mean square error (RMSE) between simulations and measurements. Error bars indicate standard error of the mean (day 9–20: *n* = 4, day 23: *n* = 8).

The simulations from the first scenario with a reflective surface of pots, soil and bottom resulted in an increase of perceived BPFD. The total height until the third node decreased under all treatments (Figure 5A) compared with the experimental chamber design (Figure 4). In the experimental design, the minimum height was reached between B260 and B310, while in the alternative scenario it was

reached between B210 and B260. The simulated length of the second and third internode (Figure 5B,C) showed that the shorter height was a result of an increase in the perceived BPFD of the second internode, where the minimum length was already reached between B160 and B210 (Figure 5B).

**Figure 5.** Simulated height until the third node (**A**) and length of second (**B**) and third (**C**) internode with a reflective surface of pots, soil and bottom.

The optimization indicated by the first scenario was applied in the second scenario by optimizing BPFD during the growth period. When the third internode started to develop the treatment changed from B210 to B260 and hereby increased BPFD. The results of the second scenario showed that increasing BPFD on day nine resulted in the minimum length of both internodes and the minimum height of 11.28 cm until the third node. The reduction in the average BPFD emitted by the LED modules resulted in a reduction of energy consumption from 107.2 W in the experimental scenario to 101.7 W in the first and 100.1 W (−7%) in the second scenario (Table 6).

**Table 6.** Average energy consumption during 23 days of growth for the three simulated scenarios to reach the minimum plant height.

