Coix lacryma-jobi L., an annual or perennial plant belonging to the Poaceae family, has long been cultivated as a food and medicine plant in China. In recent years, coix cultivation for high yields and good quality has become a research hotspot in Southwest China. Soil optimization is essential for improving crop growth. To ensure the robust establishment of coix plants, eight soil substrates, prepared from three typical soils, i.e., red clay soil, peat soil, and sandy soil, were used to cultivate two local coix varieties (Pu coix from Fujian Province, China; Qi coix from Hebei Province, China), and the plant growth and root coixol content of the two coix varieties were investigated. It was found that coix plants could maintain growth when cultivated with peat soil or sandy soil, but red clay soil was unfavorable for coix growth. The mixtures of sandy soils and peat soils resulted in synergistic benefits for coix growth and root coixol levels over the effects of sandy soil or peat soil alone. In conclusion, the mixtures of sandy soils and peat soils with appropriate proportions (sandy soils/peat soils = 2:1) were suggested as an ideal soil substrate for coix cultivation. The results provide valuable guidance for the establishment of coix plants, which could contribute to high yields and good quality in coix cultivation.

Soil salinization is a major environmental constraint that poses a significant threat to global agricultural productivity and food security. Coix lacryma-jobi L., a minor cereal crop that is valued for its nutritional and medicinal properties, displays moderate susceptibility to salinity stress. Although exogenous treatments have been demonstrated to enhance plant resilience against various biotic and abiotic stresses, the potential of nano-silicon (NaSi), melatonin (MT), and their combined application in mitigating salinity-induced damage, particularly in relation to the medicinal properties of this medicinal and edible crop, remains poorly understood. This study investigated the effects of exogenous NaSi and MT application on Coix under salinity stress using two varieties with contrasting salinity tolerances. The plants were subjected to salinity stress and treated with NaSi, MT, or a combination of both. The results revealed that salinity stress significantly impaired the agronomic traits, physiological performance, and accumulation of medicinal compounds of Coix. Exogenous MT application effectively alleviated salinity-induced damage to agronomic and physiological parameters, exhibiting superior protective effects compared to NaSi treatment. Strikingly, the combined application of MT and NaSi demonstrated synergistic effects, leading to substantial improvements in growth and physiological indices. However, the medicinal components were only marginally affected by exogenous treatments under both control and salinity-stressed conditions. Further clarification of the molecular mechanisms underlying salinity stress responses and exogenous substance-induced effects is critical to achieving a comprehensive understanding of these protective mechanisms.