Effect of Selected Physical Parameters of Lignite Substrate on Morphological Attributes, Yield and Quality of Cucumber Fruits Fertigated with High EC Nutrient Solution in Hydroponic Cultivation

Abstract

Environmentally friendly substrates that are biodegradable may provide an alternative to mineral wool, which is commonly used in hydroponic growing technology. Little is known about the relationship between the physical characteristics of lignite substrate and cucumber yield. The study analyzed the effect of bulk density and water holding capacity of lignite substrate in comparison to mineral wool and EC of nutrient solution on plant morphological parameters, yield and fruit quality of greenhouse cucumber. A positive relation was found between the bulk density of lignite mats and the increase in the number of leaves per week, shoot diameter as well as leaf length and leaf area (calculated as the product of leaf length × width) in cucumbers grown in this medium. Bulk density of lignite growing mats also affected the macro- and micro-nutrient content of cucumber leaves. The physical properties of the substrate and the high EC of the medium had a significant effect on the hardness, color and lutein content of cucumber fruits. The content of biologically active compounds in cucumber fruits depended on the water holding capacity of the medium and the water readily available to plants; these parameters were lower in the lignite medium compared to mineral wool. However, when the lignite substrate was used in hydroponic cucumber cultivation, for a period of 51 days after planting (DAP) there was an increase of more than 23% in the bulk density of the substrate and an increase of nearly 55% in the water readily available compared to the new lignite mats.