This work aimed to evaluate the growth of two species of microgreens (mizuna and pak choi), using agro-industrial compost as growing media in two different mixes versus one hundred percent peat, under two different LED illumination spectra (LED 1 and LED 2) in a 14 h photoperiod. The experiment was carried-out for two times. Biomass yield, glucosinolates, and phenolic compounds, and nitrate (NO₃⁻) content were analysed in leaf tissues. In both species, the highest fresh and dry biomass production was in compost:peat (50:50%) and LED 2 (Blue/Red/Far Red). In general, compost had a greater influence on nitrate content than light, but in the microgreen pak choi, the anthocyanin content was inhibited by the compost treatment. In the other hand both LED illumination had a positive effect on mizuna for glucosinolates and anthocyanins, and LED 2 also showed a positive effect on pak choi for anthocyanin. Therefore, the use of agri-food compost: peat (50:50%) with LED 2 (blue/red) lighting treatment to obtain microgreens in indoor crops is a plausible technology that provides nutritionally and phytochemically rich crops.

Solar radiation and the incorporation of compost into soil is a practice for disinfecting soil that could have some other effects on spinach cultivation. The quality of spinach leaves after two types of soil disinfection, non-amended soil (NAS) and compost-amended soil (CAS), was compared in order to find biomarkers of both types of disinfection. These practices did not show significant differences in nutrient composition (N-P-K) compared to the control soil (CS). However, the amount of harmful nutrients such as NO₂⁻ was significantly lower in CAS (65.74 mg kg⁻¹ FW) and NAS (49.99 mg kg⁻¹ FW) than in CS (114.39 mg kg⁻¹ FW). In addition, NO₃⁻ levels did not exceed the EU-recommended limit (<3500 mg kg⁻¹ FW). Both types of disinfected soils produced higher concentrations of total phenols and more individual flavonoids in spinach leaves than the control. Combined chemometric analysis of the HRAMS data showed different clustering depending on the type of disinfection (NAS and CAS). Fifteen metabolite compounds could be identified, seven of which are beneficial for health and were more abundant in spinach grown in CAS compared to that grown in NAS or CS. Such beneficial metabolites measured with non-target analysis as markers of CAS-grown spinach. However, more studies are necessary in order to determine the differences between the metabolites of spinach grown in NAS or CAS.

Background: Spinach has a high content of nutrients, proteins, carbohydrates, and vitamins beneficial for human health, that are closely associated with the type of crop, the growing media, the temperature, and lights used for growing. Methods: Two types of light were used: white light (WL) and red light (RL), and also three different growing media: compost without additives (CB), compost with coffee additive (CC), and compost with rockrose additive (CR). Results: Spinach grown under WL, regardless of the treatment, showed greater plant growth than that grown under RL_P. Furthermore, treatments WL_CC and WL_CR increased by 90% and 95%, respectively, compared to WL_P; similarly, treatments WL_CB, WL_CC, and WL_CR increased by 179%, 174%, and 205%, respectively, compared to the RL_P control. The protein content of spinach leaves from growing media WL_CB and WL_CC increased by 50 and 46% respectively compared to WL_P; similarly, growing media RL_CB and RL_CC increased by 82 and 57% respectively compared to RL_P. This contrasted with the carbohydrate content, which was higher in spinach grown under WL_P and RL_P. Spinach grown under WL_P and RL_P showed significantly more free sugars. On the other hand, spinach grown under WL had a higher concentration of organic acids than that grown under RL, regardless of the growing media used. The content of fatty acids, phenolic compounds, and antioxidant activities did not follow a clear pattern with respect to the type of light and growing media. Conclusions: Overall, compost-based substrates combined with white LED light enhanced spinach growth and nutritional quality through a synergistic effect. However, compost reduced phenolic compounds, while red LED light increased phenolic content and antioxidant activity, indicating contrasting effects on spinach quality.

The composting process of organic wastes involves different benefits related to their recycling, since they can contribute to obtain organic growing media alternative to peat. Moreover, these materials can show properties with added value such as biofertilizing, biostimulating, and/or biocontrol capacity. In this work, two processes of composting using agri-food wastes have been studied to determine their suitability as growing media with potential suppressive. Both the composting process and the composts obtained were evaluated by studying different chemical properties and the microbial community. The results indicated the suitability of these materials as growing media. The composition of wastes used in the composting mixtures could show the suppressive capacity of the final composts, this effect being related to the microbial community.