Trial Protocol for Evaluating Platforms for Growing Microgreens in Hydroponic Conditions
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 trial protocol 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.
The trial protocol for evaluating platforms for growing microgreens in hydroponic conditions includes the procedures to be followed and the parameters considered useful for calibrating the platform.
The procedures and parameters proposed to be included in the protocol are (Figure 1):
(1) different determinations: in controlled settings (setting the optimal ranges), and in operational environments settings (weather conditions in the area/testing period); setting the optimal ranges for microgreens, in controlled settings, between the limits of favorability for each species, aims to highlight the effects of the hydroponic platform; parameters defined and optimal ranges for different species of microgreens continuously monitored and controlled are: air temperature, water temperature, pH, electrical conductivity, relative humidity, light, nutrient content, dissolved oxygen; in order to determine whether the weather conditions in the area/testing period have an influence on the operation of the hydroponic platform, important atmospheric data will be recorded daily;
(2) procedures and parameters related to microgreen growth: obtaining the microgreens seedling, determining microgreen germination (germination energy, germination capacity, germination index), measurements on the morphology of plants, microgreens harvesting; in the case of hydroponic crops, the production of the seedling is essential in order to obtain uniform and quality microgreens;
(3) microgreens production and quality: fresh biomass yield, dry matter content, water use efficiency, bioactive compound analysis, statistical analysis.
Special attention should be paid in the testing protocol to establishing growth media for microgreens, which is one of the most important factors in the production process that influences the quality of microgreens and highlights the characteristics of the hydroponic platform.
Microgreens are young plants that are consumed at the seedling stage, which have a short production cycle (about 14 days) and require little space for growth. Microgreens are emerging functional foods of the 21st century that are gaining interest for their sustained nutraceutical properties and are an optimistic prospect for expanding especially for the consumption of the population in large urban areas and in terms of food security. Production of microgreens using hydroponic systems must be planned and controlled with care for controlling environmental factors in order to increase quality parameters. The advantages of hydroponic platforms and the development of evaluation protocols can lead to a positive influence on the quality of microgreens. This is why it is necessary to standardize certain cultivation protocols to ensure their quality. For instance, there is a wide range of environmental impact factors and variation in their relationships to downstream microgreens outputs, which means that there is no single prescription that will guarantee perfect results. The literature review has demonstrated that there are optimal ranges within which one can begin the task of designing effective prescriptions for successful microgreen production.
Many authors in the literature review have noted that best practices have not been developed, which means that although there are many guidelines for producing microgreens, we do not have very clearly defined standards.
The trial protocol aims to develop a set of procedures and parameters, included in a test protocol, for hydroponically cultivated microgreens in order to optimize the cultivation process and allow the harvest of the best possible products in any hydroponic installation. Pilot trials target research into microgreens, specifically, the influence of the crop environment and of the environment factors on the growth and development of plants under hydroponic conditions
Elaboration of the trial protocol was conducted as part of the GoHydro project (https://gohydro.org). The objective of this activity was to develop a trial protocol for hydroponic platforms for obtaining microgreens. The parameters established in the protocol have been selected so as to provide the best information on the operation of the platform. Feedback from these trials will be used for the final validation of the analytics components of the GoHydro platform.
In the protocol, we consider that microgreen growth could be characterized by four main variables that are not necessarily correlated: (1) number of growing days to reach desired size; (2) yield per area (for given number of seeds), (3) crop health (percentage of crops diseased); and (4) secondary metabolite accumulation (ascorbic acid, carotenoids, chlorophyll, etc.).
The literature review, carried out by us, with a focus on literature from the last 10 years, was conducted between November 2021 and April 2022, using the databases: Web of Sciences, Scopus, Science Direct, and Google Scholar. The established procedures and parameters are analyzed with the goal to highlight, within the tested platforms, in what way, different environment and nutritional factors (used as keywords in the review process) can influence the development of microgreens and can improve its production and quality.
The trial protocol has been developed and is to be implemented in the project for testing the GoHydro hydroponic platform.
One of the major limitations of the expansion of microgreen consumption is the rapid deterioration of their quality, which occurs immediately after harvest, thus limiting their marketing. From this point of view, the test protocol must provide a suitable platform for the hydroponic production of microgreens on different substrates, indoors, representing a sustainable alternative to conventional agriculture.
