The hydroponic production of microgreens has potential to develop, at both an industrial, and a family level, due to the improved production platforms. The literature review found numerous studies which recommend procedures, parameters and best intervals for the development of microgreens. This paper aims to develop, based on the review of the literature, a set of procedures and parameters, included in a test protocol, for hydroponically cultivated microgreens. Procedures and parameters proposed to be included in the trial protocol for evaluating platforms for growing microgreens in hydroponic conditions are: (1) different determinations: in controlled settings (setting the optimal ranges) and in operational environments settings (weather conditions in the area/testing period); (2) procedures and parameters related to microgreen growth (obtaining the microgreens seedling, determining microgreen germination, measurements on the morphology of plants, microgreens harvesting); (3) microgreens production and quality (fresh biomass yield, dry matter content, water use efficiency, bioactive compound analysis, statistical analysis). Procedures and parameters proposed in the protocol will provide us with the evaluation information of the hydroponic platforms to ensure: number of growing days to reach desired size; yield per area, crop health, and secondary metabolite accumulation.
Lettuce microgreens are one of the most popular vegetables due to them being perceived as a “healthy food”, with high concentrations of nutrients, beneficial vitamins, and minerals. With a short vegetation period, they can be cultivated with minimum investment, and they are increasingly accepted by consumers, as they are healthy and easy to prepare. Lettuce has high ecological plasticity, but, despite this, its phenotypic expression, morphology, physiology, and anatomy are significantly influenced by environmental conditions. Lettuce microgreens contain higher quantities of phytonutrients and minerals and lower quantities of nitrates at the early stage of development than at the completely developed stage. The environmental conditions that influence the development of lettuce microgreens (and their quality) in a hydroponic system are as follows (average ideal values): light (400 W), photoperiodicity (12 h), light intensity (400 µmol m−2 s−1), colour spectrum (440-460 nm), temperature (20 ± 2 °C), and humidity (80 ± 5 %). The nutritional solution in a hydroponic system must be carefully monitored, by checking certain essential parameters such as the following (average ideal values): pH (6.3 ± 0.4), electrical conductivity (1.8 ± 0.2 mS), dissolved oxygen (6 mg L−1), and temperature (18 ± 2 °C). The analysis of expert literature reveals that there is a need to establish certain protocols for cultivating microgreens in hydroponic systems, to minimize the factors that can negatively influence the plants, in order to obtain higher concentrations of active substances.
Basil (Ocimum basilicum L.), including other species and cultivars, is an excellent source of nutritional compounds, the accumulation of which can be stimulated by exogenous factors (environmental and nutritional conditions). Although best practices are relatively established for mature basil plants, microgreens production requires further research to optimize quality and quantity. The study objectives are (i) to provide an overview of the many uses of basil, (ii) collate and present common hydroponic systems available in the market, (iii) review effects of key production environment parameters on basil yields in hydroponic systems, and (iv) summarize the effects of the growth environments on yield quantity and quality of basil microgreens. The paper analyzes in detail key production parameters of basil microgreens in hydroponic systems, such as temperature, humidity, pH, electrical conductivity, dissolved oxygen, carbon dioxide, nutrient solutions, and the influence of light (quantity, quality, and photoperiods). The collated literature review has shown that basil, grown hydroponically, can tolerate high variations of environmental parameters: pH 5.1–8.5, temperature 15–24 °C, relative humidity 60–70%, electrical conductivity up to 1.2 mS cm−1, depending on the developmental stage, dissolved oxygen at 4 mg L−1 (optimally 6.5 mg L−1), and light intensity between 200 and 400 μmol m−2 s−1. The study has synthesized an overview of different production parameters to provide guidance on the optimization of environmental conditions to ensure the quantity and quality production of basil microgreens. Improving the quality of basil microgreens can ideally spur continued gastronomic interest in microgreens in general, which will encourage more entrepreneurs to grow basil and other microgreens. Hence, the study findings are a great resource to learn about the effects of different environments on basil microgreen production. This information can inform research for successful production of different species and cultivars of basil microgreens, and establishing testing protocols to improve the quantity and quality of the harvest.