In recent years, much effort has been devoted to understanding the response of plants to different light properties, largely due to advances in the light-emitting diode (LED) industry. This work studied the effect of different light intensities and qualities on yield or quality of indoor hydroponic spinach (Spinacia oleracea L.). Two trials were carried out at two different times. The intensity assay was carried out with the same type of light (AP673L, Valoya Ltd., Helsinki, Finland) at different luminous intensities (150, 290, and 430 µmol m⁻² s⁻¹). In the second trial, four different luminance spectra (Valoya Ltd., Helsinki, Finland) were used (NS12, AP67, AP673L, G2). Then, the fresh and dry weight, nutritional status, and concentration of primary metabolites were determined. Both lights parameters induced changes in vegetative performance and other physiological traits, as well as their quality and nutritional composition (minerals, organic acids, sugars, and amino acids). The increase in light intensity increased Fv’/Fv’, fresh weight, leaf area, chlorophyll fluorescence parameters, and potassium concentration. The light intensity effectively controlled nitrate accumulation in an inverse relationship. The effect of the light spectrum on spinach characteristics was not clearly observed when multivariate statistics were applied to the data. No linear relationship was found between the different R/B ratios. This is perhaps due to commercial lights having a complex combination of wavelengths, in addition to the main R/B proportion. Within the overall results, 6 R/B presented the best results for the indoor cultivation of spinach. More studies are needed, since breeding for controlled environments shifts the focus of the desired crop attributes towards rapid growth and harvest quality instead of stress adaptability.

Due to the edaphoclimatic conditions in southeast Spain, which are expected to worsen due to climate change, more efficient ways of using water must be found to maintain sustainable agriculture. Due to the current high price of irrigation control systems in southern Europe, 60–80% of soilless crops are still irrigated, based on the experience of the grower or advisor. The hypothesis of this work is that the development of a low-cost, high-performance control system will allow small farmers to improve the efficiency of water use by obtaining better control of soilless crops. The objective of the present study was to design and develop a cost-effective control system for the optimization of soilless crop irrigation after evaluating the three most commonly used irrigation control systems to determine the most efficient. Based on the agronomic results comparing these methods, a prototype of a commercial smart gravimetric tray was developed. The device records the irrigation and drainage volumes and drainage pH and EC. It also offers the possibility of determining the temperature, EC, and humidity of the substrate. This new design is scalable thanks to the use of an implemented data acquisition system called SDB and the development of software in the Codesys programming environment based on function blocks and variable structures. The reduced wiring achieved by the Modbus-RTU communication protocols means the system is cost-effective even with multiple control zones. It is also compatible with any type of fertigation controller through external activation. Its design and features solve the problems in similar systems available on the market at an affordable cost. The idea is to allow farmers to increase their productivity without having to make a large outlay. The impact of this work will make it possible for small-scale farmers to have access to affordable, state-of-the-art technology for soilless irrigation management leading to a considerable improvement in productivity.

Agro-food sector byproducts are valuable sources of biostimulants. Alperujo, the primary by-product generated during the two-phase centrifugation process of olive oil extraction, is rich in bioactive compounds, particularly phenolic compounds, which could enhance its valorization potential. Among these, hydroxytyrosol-4-glucoside and hydroxytyrosol were the predominant phenolic compounds detected. Despite the well-documented antioxidant and health-promoting properties of hydroxytyrosol, there is a notable lack of studies evaluating its use as a biostimulant in agricultural applications. To address this gap, the present study evaluated the agronomic and qualitative responses of tomato plants to the application of two commercial hydroxytyrosol-rich formulations (formulas A and B) derived from olive oil extraction by-products. Tomato plants were cultivated under greenhouse conditions using a soilless coco peat substrate, and the formulations were applied via the root system at different doses and application times, following the manufacturer's recommendations. Formulae A and B contained hydroxytyrosol at concentrations of 2.8 mg mL−1 and 6.4 mg mL−1, respectively. Key production parameters, including yield, fruit size, and number of fruits, both marketable and nonmarketable, were recorded. Additionally, fruit quality attributes were assessed, including shelf life, firmness, total soluble solids (TSS), antioxidant capacity, and concentrations of lycopene, vitamin C, total polyphenols, and anthocyanins. Formula B also increased fruit Ca, K and N concentrations, suggesting enhanced nutrient partitioning towards fruits. Metabolomic analysis of fruit tissues was performed using NMR spectroscopy to quantify primary metabolites, including sugars, organic acids, and amino acids, in the fruit. The results demonstrated that the application of these biostimulant formulations enhanced crop yield. Formula B increased the total and marketable yields by 15.7% and 21%, respectively, and formula A by 9.6% and 14.5%, respectively. Fruit firmness improved by up to 30%, and shelf life was extended by 37% and 54% with the use of formulas A and B, respectively. In addition, the key antioxidant attributes were improved. Lycopene increased by 36% and 21% under formula A and B, respectively. Total vitamin C increased by 18% with Formula B. Sugar content (glucose and fructose) and malate concentrations were significantly higher in treated fruits, whereas glutamine levels increased by 67% with Formula B. These findings highlight the potential of hydroxytyrosol-rich biostimulants to improve tomato yield, fruit quality, and postharvest longevity while promoting sustainable agriculture and the valorization of agro-industrial waste.

Agro-food processing by-products represent valuable sources of bioactive compounds with potential applications in sustainable crop production. This study evaluated the agronomic and postharvest responses of greenhouse-grown tomato to two commercial formulations enriched in hydroxytyrosol (Formula A and Formula B) and derived from olive oil processing by-products. Plants were grown in a soilless coco-peat system, and the formulations were applied manually to the root system according to their respective manufacturer-recommended regimes. The substrate bag was considered the experimental unit (n = 6 per treatment), with the greenhouse block retained in the statistical model. Formula A and Formula B increased total yield by 9.6% and 15.7%, respectively, and marketable yield by 14.5% and 21.0%. Both formulations increased fruit firmness, whereas total soluble solids remained unaffected. Shelf life increased from 23 days in control fruit to 32 and 38 days following Formula A and Formula B application, respectively. Antioxidant-related responses were treatment-dependent: Formula B increased DPPH radical-scavenging capacity and total and reduced vitamin C, whereas lycopene increased significantly with Formula A and showed an intermediate response with Formula B; total polyphenols and anthocyanins were unaffected. The treatments also modified fruit primary-metabolite profiles, including sugars, organic acids, and amino acids, and both formulations increased fruit Ca, K, and N concentrations at the final sampling. Overall, these findings demonstrate the potential of hydroxytyrosol-enriched commercial formulations to improve tomato productivity and selected postharvest-quality traits while providing a valorization route for olive oil processing by-products. However, because the formulations differed in composition, hydroxytyrosol concentration, dose, and application frequency, the specific contribution of hydroxytyrosol cannot be isolated from that of the complete formulations.