Hydroponic vs. soil cultivation of lettuce and spinach: A study in a polycarbonate greenhouse at high altitudes in the Trans-Himalayan region

Abstract: This study compared the hydroponic and soil cultivation systems for lettuce and spinach production in India’s cold desert, high-altitude Trans-Himalayan region. Hydroponic cultivation is a soilless technique that provides fresh vegetables in regions with environmental stress and limited arable land. The experiment was conducted in hydroponic structures designed for leafy vegetable cultivation, including vertical and horizontal circulated nutrient film technique (NFT), non-circulated systems, and soil cultivation in an open, naturally ventilated double-layer polycarbonate greenhouse in Ladakh, India. Results showed that lettuce and spinach grown in the vertical circulated NFT system had significantly better plant growth characteristics such as plant height, number of leaves, leaf area, fresh weight, and yield than horizontal NFT, non-circulated, and soil systems. Moreover, fresh produce from vertical and horizontal NFT systems had higher nitrate content, soluble sugar content, and total sweetness index, indicating better crispiness of the produce. Mineral nutrient contents (Ca, Mg, B, Cu, Mn, Zn, Fe, and Ni) were also higher in the circulated NFT system compared to other systems studied. Thus, this study demonstrated that lettuce and spinach grown in NFT systems produced significantly higher yields with better nutritional quality than soil-grown systems in the Trans-Himalayan region. Hydroponic systems are recommended for successfully producing nutrient-rich vegetables in areas with limited water and arable land. This is the first demonstration of hydroponic systems in high-altitude cold desert conditions for growing leafy greens, and it has promising implications for sustainable agriculture.