Indoor production systems with light emitting diode (LED) lamps are a feasible alternative for increasing strawberry productivity by reducing the incidence of pests and diseases and the damage caused by extreme weather events. Blue (BL) and red (RL) LED light are considered the most important light spectra for photosynthesis and crop yield; however, recent studies have demonstrated that the beneficial effects of green light (GL) have been underestimated. This information would be of particular importance for strawberry production in controlled-environments/vertical farming systems as it may lower input costs and enhance production efficiency and quality and marketability. The present study aimed to define the effect of GL in combination with BL in strawberry. A proportion of 20% GL (20% BL + 60% RL) of total photosynthetic photon flux density was beneficial for plant growth and productivity; however, a 27% GL (12% BL + 61% RL) proportion was detrimental or comparable to that with 6% GL (36% BL + 58% RF). Total dry mass increased 51% when plants were illuminated with 20% GL lamps compared to those with 6% GL; the most impacted plant part was the root as it increased by 155%. The higher yield was observed with GL at 20%, but further increasing GL to 27% resulted in reduced yield. GL at 20% and 27% exhibited higher photosynthesis but reduced transpiration, stomatic conductance, and internal CO₂, which in turn increased instantaneous and intrinsic water-use efficiency. Plants with the highest yield (20% GL) exhibited lower total soluble solids in fruits but still the values obtained were acceptable (8.25 °Brix); these fruits contained a high total sugars and phenolics concentration but a reduced antioxidant scavenging capacity. High proportions of GL were associated with a higher leaf and fruit Ca and a higher leaf P and K, which may be due to the increased allocation of biomass to the roots. In conclusion, GL at 20% and BL at 20% resulted in the best growth and yield parameters, enhanced net photosynthesis rate, water-use efficiency and fruit quality attributes. The effects of GL observed in this study may also be important for other high-value horticultural crops suitable for indoor vertical farming.

Salinity is a major threat to the productivity of agroecosystems as it affects the soil structure and the osmotic potential of the soil solution, resulting in nutritional imbalances, Na toxicity and reduction in crop growth and yield. As Silicon (Si) has been considered a beneficial element for alleviating plant stress, the present study was performed to determine if it could enhance tomato plant tolerance to NaCl-salinity in a closed-loop hydroponic system. Plants were irrigated with solutions containing 0, 20 or 60 mM NaCl combined with 0 or 1.50 mM Si. Shoot dry weight and fruit yield decreased with salinity, however, Si partially restored biomass and yield when the solutions contained 20 mM NaCl. Shoot and root K decreased with salinity, however, supplementary Si restored K in plants with 60 mM NaCl. Root and shoot Si was unaffected by NaCl or Si, however, shoot Na increased. Nonetheless, compared to non-Si plants, Si-treated plants showed a 19% and 32% lower shoot Na concnetration in 20 and 60 mM NaCl-plants, respectively. Silicon partly alleviated the K/Na imbalance caused by salinity. Increased shoot K/Na and Ca/Na balances were correlated with higher shoot biomass. Supplemental Si allowed an 80% increase in peroxidase activity and proline in plants with 60 mM NaCl. Fruit yield under moderate salinity was partially restored by Si, due to an increased root Na exclusion, lower shoot Na, and improved K, Ca and K/Na balance, which was correlated with increased shoot growth, POD activity and proline concentration.

Blueberry is a highly demanded and consumed fruit due to its beneficial effects on human health, because of its bioactive compounds with a high antioxidant capacity. The interest in increasing the yield and quality of blueberries has led to the application of some innovative techniques such as biostimulation. The objective of this research was to assess the effect of the exogenous application of glutamic acid (GLU) and 6-benzylaminopurine (6-BAP) as biostimulants on flower bud sprouting, fruit quality, and antioxidant compounds in blueberry cv. Biloxi. The application of GLU and 6-BAP positively affected bud sprouting, fruit quality, and antioxidant content. The application of 500 and 10 mg L⁻¹ GLU and 6-BAP, respectively, increased the number of flower buds, while 500 and 20 mg L⁻¹ generated fruits with higher content of flavonoids, vitamin C, and anthocyanins and higher enzymatic activity of catalase and ascorbate peroxidase enzymes. Hence, the application of these biostimulants is an effective way to enhance the yield and fruit quality of blueberries.

Greenhouse cultivation is highly efficient in the use of water and fertilizers. However, due to intensive production, the greenhouse industry applies ample amounts of water and fertilizers. An alternative to minimize water and nutrient loss is zero-leaching systems, such as closed-loop subirrigation. The objective of the present study was to compare the water and fertilizer use efficiency in containerized tomato plants grown in a subirrigation system and a drip irrigation system. Subirrigated plants exhibited lower biomass than drip-irrigated plants. However, the amount of nutrient solution required to restore evapotranspirated water was lower in subirrigation. The yield was marginally decreased in subirrigated plants compared to drip-irrigated plants. The amount of nutrient solution required to produce 1 kg of fresh tomatoes was 22 L in subirrigation, whereas in drip irrigation, plants demanded 41 L. The total nitrogen applied through the nutrient solution was 75% lower in subirrigation than in drip irrigation, while the phosphorus, potassium, calcium and magnesium applied was 66%, 59%, 70% and 74% lower, respectively. We concluded that the subirrigation system proved to be more water- and nutrient-efficient than the drip irrigation system due to the zero leaching of the nutrient solution, the lower number of irrigation events required and the lower nutrient demand of plants.

Sub-irrigation of greenhouse crops has the potential to increase water and nutrient use efficiency; however, fertilizer salts that are not absorbed by the plants tend to accumulate in the substrate and eventually raise the substrate’s electrical conductivity (EC). The objective of this study was to determine the optimum EC of the nutrient solution in sub-irrigated tomatoes to allow maximum yield. Total fruit yield was higher in sub-irrigated plants with solutions at 2.0 dS m⁻¹ (5105 g per plant), and it was comparable to that obtained for drip-irrigated plants (4903 g per plant); however, the yield of fruits from the second truss was 37% higher in sub-irrigated than in drip-irrigated plants when the EC was 2.0 dS m⁻¹. In contrast, at the end of the growing season, the yield of plants sub-irrigated with nutrient solutions of 2.0 dS m⁻¹ was the lowest, being surpassed by 37% by that of plants treated with 1.4 dS m⁻¹. The dry weight of vegetative plant parts was reduced in sub-irrigated plants, suggesting a shift in dry mass partitioning. Our results show that with sub-irrigation, the growing season should be started using nutrient solutions with higher EC, but eventually, this EC should be decreased to maintain proper substrate EC and high yield.

The strawberry fruit (Fragaria × ananassa Duch.) is appreciated for its aroma, color, texture and nutritional value. In conventional agriculture, the use of fertilizers damages the environment since it causes loss of soil fertility, salinity and its erosion, hence production alternatives, without harming the environment, are sought. The objective of this study was to evaluate the effect of a biostimulant based on humic substances and rhizobacteria, on the production and quality of the strawberry cultivar ‘San Andreas’. Strawberry plants cultivar ‘San Andreas’ were treated with fulvic acids + mixture of microorganisms, humic acids + Pseudomonas fluorescens, fulvic acids + Azospirillum brasilense, fulvic acids + Pseudomonas fluorescens and the mixture AH and AF + Azospirillum brasilense with two doses (d1, d2) in total 10 treatments were applied plus the control. Humic substances were applied every 15 days and rhizobacteria every 30 days. The results showed that the AFyAzoz d1 increased over control plants, the number of leaves in 38.3%, root volume in 42.6%, the fresh weight in 130% and dry weight in 63.8%, the number of fruits 50.0% and the yield in 59.5%. The AFyPF d1 favored Photosynthesis in 127.3%; AFyPF d1 increased TSS in 25%, AFyPF d2 vitamin C in 17.1% and MHyF + Azoz d1 increased in 20% the content of Phenols. Humic substances plus rhizobacteria are an ecological alternative to be used as biostimulant in the production and quality of strawberry plants.