The goal of this research was to investigate the effect of electrical conductivity (EC) levels of the nutrient solution on the fresh weight, chlorophyll, and nitrate content of hydroponic-system-grown lettuce. The selected cultivars are the most representative commercial varieties grown for European markets. Seven cultivars (‘Sintia,’ ‘Limeira,’ ‘Corentine,’ ‘Cencibel,’ ‘Kiber,’ ‘Attiraï,’ and ‘Rouxaï’) of three Lactuca sativa L. types’ (butterhead, loose leaf, and oak leaf) were grown in a phytotron in rockwool, meanwhile the EC level of the nutrient solutions were different: normal (<1.3 dS/m) and high (10 dS/m). The plants in the saline condition had a lower yield but elevated chlorophyll content and nitrate level, although the ‘Limeira’ and ‘Cencibel’ cultivars had reduced nitrate levels. The results and the special characteristic of the lollo-type cultivars showed that the nitrate level could be very different due to salinity (‘Limeira’ had the lowest (684 µg/g fresh weight (FW)) and ‘Cencibel’ had the highest (4396 µg/g FW)). There was a moderately strong negative correlation (−0.542) in the reverse ratio among the chlorophyll and nitrate contents in plants treated with a normal EC value, while this relationship was not shown in the saline condition. Under the saline condition, cultivars acted differently, and all examined cultivars stayed under the permitted total nitrate level (5000 µg/g FW).

Urban gardens are spreading in many cities across Europe, with community gardening being a fundamental form of urban agriculture. While the literature reveals the essential role that community gardens can play in terms of learning and education, no studies have investigated the training needs for participants in community gardens to ensure their successful development. The goal of this article is to evaluate the training requirements of urban community gardens to ensure their successful implementation and their contribution to sustainability in European cities. Two questionnaires of users’ needs analysis were designed and implemented in Berlin, Bologna, Budapest, and Cartagena. The results unveiled the need to re-enforce the training in the formation and community building phases of community gardens towards ensuring the creation of an engaged gardening community to maintain activity, particularly for top-down activities (e.g., research-related gardens). Users claimed their need for being trained on crop management skills (e.g., maintenance, bed preparation, organic practices) and on communication skills to further disseminate their activity, thereby increasing the potential for citizen engagement. Such requirements could be overcome with the creation of urban gardens networks, where experiences and knowledge are shared among practitioners. Policy recommendations are provided based on the outputs of this study.

Grafting by vegetables is a practice with many benefits, but also with some unknown influences on the chemical composition of the fruits. Our goal was to assess the effects of grafting and storage on the extracted juice of four orange-fleshed Cantaloupe type (Celestial, Donatello, Centro, Jannet) melons and two green-fleshed Galia types (Aikido, London), using sensory profile analysis and analytical instruments: An electronic tongue (E-tongue) and near-infrared spectroscopy (NIRS). Both instruments are known for rapid qualitative and quantitative food analysis. Linear discriminant analysis (LDA) was used to classify melons according to their varieties and storage conditions. Partial least square regression (PLSR) was used to predict sensory and standard analytical parameters. Celestial variety had the highest intensity for sensory attributes in Cantaloupe variety. Both green and orange-fleshed melons were discriminated and predicted in LDA with high accuracies (100%) using the E-tongue and NIRS. Galia and Cantaloupe inter-varietal classification with the E-tongue was 89.9% and 82.33%, respectively. NIRS inter-varietal classification was 100% with Celestial variety being the most discriminated as with the sensory results. Both instruments, classified different storage conditions of melons (grafted and self-rooted) with high accuracies. PLSR showed high accuracy for some standard analytical parameters, where significant differences were found comparing different varieties in ANOVA.

Mushroom cultivation is an important branch of the agricultural industry, and global mushrooms production has increased more than sixfold in the last decade. This industry uses large amounts of agricultural, forestry, livestock, and industrial wastes and their by-products. However, it also generates millions of tons of spent mushroom compost (SMC) (approximately 100 million tons per year) which has emerged as a significant issue that hinders the growth of the mushroom business and impacts the environment. Many crop diseases, which cause significant economic losses, are introduced by soil-borne plant pathogens. Spreading spent mushroom compost (SMC) to agricultural soils is a natural way to control plant diseases. Using organic waste material instead of chemicals, which is the most widely used method in agriculture today, is also a more environmentally responsible option. The generated SMC can potentially be used as a soil conditioner, an organic fertilizer, and suitable medium for growing various vegetable crops. The application of SMC has been found to be beneficial in the control of crop diseases by inducing microbiostasis, direct toxicity, or by inducing systemic resistance of the host plant. In the current review, the practical application of SMC in the cultivation of tomato, pepper, lettuce, cucumber, and eggplant was addressed. The application of SMC as a soil amendment showed a significant improvement in soil properties, including soil NPK, organic matter content, and soil beneficial microorganisms. Our review indicated that SMC could be used as a low-cost, alternative growing medium in vegetable production or as a soil amendment to add nutrients and restore soil fertility in agricultural lands. The SMC may be able to replace peat, a non-renewable natural resource, and thereby mitigating the adverse effects of excessive peat extraction in wetlands, bogs, marshes, and peatlands. This review uses unique data on the effective use of SMC in agricultural disease management, reducing the need for chemical pesticides that have adverse effects on both the environment and human health. It also provides a safe method for reusing, recycling, and integrating SMC into a circular economy that reduces its negative environmental effects and carbon footprint impacts. This work also offers a novel application of SMC as a low-cost substitute for peat or other growing media that pose environmental risks. Graphical abstract

Vegetable grafting is considered a rapid, non-chemical alternative method to relatively slow and expensive breeding to overcome the adverse effect of salinity. Therefore, a soilless experiment was performed to determine the salinity tolerance of eggplant (Solanum melongena) cv. Madonna grafted onto two different rootstocks, Solanum grandifolium × Solanum melongena (SH) and Solanum torvum (ST), as well as self-grafted (SG) and self-rooted (SR) as controls. All groups of plants were treated with 0 mM NaCl or 80 mM NaCl. A significant decrease in the relative leaf chlorophyll content (SPAD value) and chlorophyll concentrations were found in response to NaCl. However, the grafted plants had a higher photosynthetic pigment level than the non-grafted plants grown under saline conditions. Grafting eggplants onto SH significantly enhanced the total fruit yield as compared to the self-rooted plants exposed to salinity by increasing the average fruit weight. Moreover, salt stress significantly increased the whitening index and oxidation potential of fruits. The plants grafted onto SH or ST accumulated more Na⁺ in their roots than in their fruit or leaves, thus the Na⁺ partitioning between the above-ground and root parts most probably determines the increased salinity tolerance of the grafted ST and SH plants. To conclude, both the SH and ST rootstocks protected the scions against salinity; the scion showed both increased photosynthetic pigment concentration and chlorophyll fluorescence parameters as well as a lower Na⁺ concentration under stress that resulted in a higher fruit yield and quality.

Abiotic stresses have been observed to cause alterations in the morphology, physiology, and biochemistry of plants. However, in recent years, the utilization of nanocompounds has emerged as a strategy to induce modifications in multiple facets of plant biology. These modifications include plant growth, nutrient absorption, the production of significant secondary metabolites, and the improvement of plants’ resistance against both abiotic and biotic stress factors. A completely randomized factorial experiment with 12 replications was created. Potassium sources including control, potassium (K), and nanocapsule-potassium (N-K) with concentration 1 µM and temperature treatments including control temperature (25 °C) and high-temperature stress (35 °C) were applied as treatments. In the control treatment, proline was increased at the high temperature, whereas proline was reduced at both treated temperatures by K and N-K. High temperature raised electrolyte leakage (EL), which peaked in the control treatment but was lowered by K and N-K. Temperature-dependent increase in glucose and fructose was observed in control and K treatments when the temperature was 35 °C, but no significant difference was observed between different levels of K at 35 °C. When K was not applied at high temperatures, the main stress indicators such as antioxidant activity (DPPH) and malondialdehyde (MDA) rose significantly, as did the water potential and linoleic acid. When high temperatures were applied, nanocapsule-potassium applied in high temperatures had the lowest stress indices. In conclusion, stress indices diminish when nanocapsule-potassium is applied under high temperatures. Additionally, nanocapsule-potassium applied at high temperatures was preferable to K applied at high temperatures in terms of pepper growth and resistance measures. Likewise, the application of nanocapsule-potassium at high temperatures alters the fatty acid composition of membranes and antioxidant enzymes.