Vertical farming for lettuce production in limited space: a case study in Northern Thailand.

Background: Greenhouse vertical farming under natural sunlight is an alternative farming technique that grows crops in a stacking column and extends in a vertical direction. Sunlight availability is one of the crucial factors for crop development in vertical farming. Therefore, this investigation aimed to examine the effect of sunlight availability on lettuce growth and yields at different levels of vertical shelves. Methods: Six shelves were constructed with three levels: upper, middle and lower levels. Lettuces (Lactuca sativa L.) as 'Baby Cos' and 'Green Oak' at 14 days after sowing were planted on the three levels. The photosynthetic photon flux density (PPFD) was recorded, and the PPFD values were then converted to the daily light integral (DLI). Plant height and canopy width were measured three times at 14, 21 and 28 days after transplanting. At maturity, fresh weight (FW) was directly monitored after harvest. Results: The results showed that the highest PPFD and DLI values were found at the upper level (PPFD 697 µmol m-2 s-1 and DLI 29 mol m-2 d-1) in comparison to the middle (PPFD 391 µmol m-2 s-1 and DLI 16 mol m-2 d-1) and lower (PPFD 322 µmol m-2 s-1 and DLI 13 mol m-2 d-1) levels. The lowest plant height and canopy width values were observed on the upper levels for both lettuce varieties during the three measurement dates. The middle ('Baby Cos' = 123.8 g plant-1 and 'Green Oak' = 190.7 g plant-1) and lower ('Baby Cos' = 92.9 g plant-1 and 'Green Oak' = 203.7 g plant-1) levels had the higher values of FW in comparison to the upper level ('Baby Cos' = 84.5 g plant-1 and 'Green Oak' = 97.3 g plant-1). The values of light use efficiency (LUE) showed an increased trend from the upper to lower levels in both varieties, with values of 'Baby Cos' of 0.10 g mol-1 in the upper level, 0.28 g mol-1 in the middle level and 0.26 g mol-1 in the lower level and 'Green Oak' of 0.12 g mol-1 in the upper level, 0.44 g mol-1 in the middle level and 0.57 g mol-1 in the lower level. The findings of the study indicated the viability of utilizing vertical shelves for lettuce production.

Dual-bioaugmentation strategy to enhance the formation of algal-bacteria symbiosis biofloc in aquaculture wastewater supplemented with agricultural wastes as an alternative nutrient sources and biomass support materials.

This study performs an integrated evaluation of the formation and distribution of algal-bacterial bioflocs in aquaculture wastewater supplemented with agricultural waste, together with an assessment of their behavior in the microbial community and of the water quality of the system in which a new bioaugmentation strategy was applied. Results indicated that the dual bioaugmentation strategy via the consortium addition of bacteria and microalgae had the highest formation performance, providing the most compact biofloc structure (0.59 g/L), excellent settleability (71.91%), and a large particle diameter (4.25 mm). The fed-batch supplementation of molasses and rice bran, in terms of changes in the values of COD, NH4+, NO3-, and PO43-, stimulated the formation of biofloc through algal-bacterial bioflocs and microbe-rice bran complexes within a well-established microbial community. These findings provide new insight into the influence of bioaugmentation on the formation of an innovative algal-bacterial biofloc.