Effects of growing systems, far-red radiation and planting density on lettuce cultivation

Vertical farms (VFs) are innovative urban production facilities consisting of multi-level indoor systems equipped with artificial lighting in which all the environmental conditions are controlled independently from the external climate.

VFs are generally provided with a closed-loop fertigation system to optimize the use of water and nutrients. The objective of this study, performed within an experimental VF at the University of Bologna, was to quantify the water use efficiency (WUE, ratio between fresh plant weight and the volume of water used) for lettuce (Lactuca sativa L.) growth cycle obtained in two different growing systems: an ebb-and-flow substrate culture and a high-pressure aeroponic system. Considering the total water consumed (water used for irrigation and climate management), the WUE of ebb-and-flow and aeroponics was 28.1 and 52.9 g L−1 H2O, respectively.

During the growing cycle, the contribution generated by the recovery of internal air moisture from the heating, ventilation, and air conditioning (HVAC) system was quantified. Indeed, by recovering water from the dehumidifier, water use decreases dramatically (by 67 %), while WUE increases by 206 %. Further improvement of WUE in the ebb-and-flow system was obtained through ameliorated crop management strategies, in particular, by increasing planting densities (e.g., 153, 270, and 733 plants m−2) and by optimizing the light spectrum used for plant growth (e.g., adjusting the amount of far-red radiation in the spectrum).

Strategies for efficient use of water in high-tech urban indoor growing systems are therefore proposed.

Carotti, L., Pistillo, A., Zauli, I., Meneghello, D., Martin, M., Pennisi, G., Gianquinto, G., & Orsini, F. (2023). Improving water use efficiency in vertical farming: Effects of growing systems, far-red radiation and planting density on lettuce cultivation. Agricultural Water Management, 285, 108365. https://doi.org/10.1016/j.agwat.2023.108365  

Read the complete paper at sciencedirect.com

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