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. 2016 Aug;5(3):184-191.
doi: 10.1002/fes3.83. Epub 2016 Jun 6.

Vertical farming increases lettuce yield per unit area compared to conventional horizontal hydroponics

Dionysios Touliatos  1 , Ian C Dodd  1 , Martin McAinsh  1
Affiliations

Vertical farming increases lettuce yield per unit area compared to conventional horizontal hydroponics

Dionysios Touliatos et al. Food Energy Secur. 2016 Aug.

Abstract

Vertical farming systems (VFS) have been proposed as an engineering solution to increase productivity per unit area of cultivated land by extending crop production into the vertical dimension. To test whether this approach presents a viable alternative to horizontal crop production systems, a VFS (where plants were grown in upright cylindrical columns) was compared against a conventional horizontal hydroponic system (HHS) using lettuce (Lactuca sativa L. cv. "Little Gem") as a model crop. Both systems had similar root zone volume and planting density. Half-strength Hoagland's solution was applied to plants grown in perlite in an indoor controlled environment room, with metal halide lamps providing artificial lighting. Light distribution (photosynthetic photon flux density, PPFD) and yield (shoot fresh weight) within each system were assessed. Although PPFD and shoot fresh weight decreased significantly in the VFS from top to base, the VFS produced more crop per unit of growing floor area when compared with the HHS. Our results clearly demonstrate that VFS presents an attractive alternative to horizontal hydroponic growth systems and suggest that further increases in yield could be achieved by incorporating artificial lighting in the VFS.

Keywords: Land use efficiency; plant factory; urban agriculture; vertical column grower..

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Figures

Figure 1
Figure 1
Schematic shows planting densities within the HHS and VFS. (A) Overhead view of HHS. (B) Side‐view of VFS. (C) Overhead view of VFS. The HHS occupied 0.4 m2 of growing floor area, whereas the VFS occupied 0.02 m2 per column of floor area. The grey rectangles show the exact position of the 400 W metal halide lamps above the growth systems. The grey circles within the VFS show the exact measurement positions of the Macam Q203 Quantum radiometer quantum sensor. Light measurements in the HHS were obtained directly above the plants, at 20 cm distance from the PVC pipes. Scale bar is 20 cm. VFS, vertical farming system; HHS, horizontal hydroponic system.
Figure 2
Figure 2
Linear regression analysis of shoot fresh weight versus layer in the VFS (solid line; closed symbols) and HHS (open symbols), respectively. When the linear regression was not significant the regression line was omitted. The regression equation, adjusted R 2 values and significance of the regression (P‐value) are reported at the top of the panel. VFS, vertical farming system; HHS, horizontal hydroponic system.
Figure 3
Figure 3
PPFD within the vertical farming system (VFS; closed symbols) and the horizontal hydroponic system (HHS; open symbols) plotted against layers in the growth systems. Values indicated with different letters indicate statistically significant differences, whereas those marked with the same letters show statistically similar values. Error bars represent SE (n = 8). VFS, vertical farming system; HHS, horizontal hydroponic system; PPFD, photosynthetic photon flux density.
Figure 4
Figure 4
Linear regression analysis of shoot fresh weight versus PPFD in the vertical farming system (VFS; solid line; closed symbols) and horizontal hydroponic system (HHS; open symbols), respectively. When the linear regression was not significant the regression line was omitted. The regression equation, adjusted R 2 values, and significance of the regression (P‐value) are reported at the top of the panel. VFS, vertical farming system; HHS, horizontal hydroponic system; PPFD, photosynthetic photon flux density.
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