A middle range portable scanning lidar was applied from a 10-m height place to estimate vertical plant area density (PAD) profiles of rice canopy at different growth stages. Voxel-based canopy profiling method was applied for the estimation. Resultant PAD estimates showed over estimation at middle to lower layers with the root mean square errors of 0.36, 0.45, 0.95, 1.81 m2m-3 in each stage. Laser beam coverage index Ω was calculated and related to absolute errors of PAD to investigate causes of the errors. This showed that lack of the number of incident laser beams into the internal canopy was a major cause of the error. Although the lidar-derived PAD showed overestimation in middle to lower layers, the PAD estimates of upper layers agreed well with the actual values. The accurate PAD estimates of upper five layers could offer good correlation to dry weight of ears with R2=0.988.
Acoustic emission (AE) was measured at the stem of a cherry tomato in spray culture, and the change ratio of AE before and after irrigation RD was calculated. The AE event rate highly fluctuated, and the number of detected AEs was insufficient to calculate RD at all times. However, the change in RD was negatively related to the increase and decrease in irrigation time for a short duration (less than 5 h), while the change of RD contrarily showed positive relationship with the irrigation time in a long term. Furthermore, the yield and sugar content of the fruits were related to the average value of RD. These results suggest that RD might improve the efficiency of tomato cultivation in a horticultural facility.