Effect of Different Soil Textures and Medicinal Solid Wastes on Growth Performance of Spinach

Synthetic production of essential oils results in significant amounts of solid waste, the disposal of which is associated with environmental risks. The present study evaluated the potential of using mallow (<i>Althaea officinalis</i>), thyme (<i>Thymus vulgaris</i>), and nettle (<i>Urtica dioica</i> L) medicinal plant wastes after oil distillation as organic amendments in different soil textures for spinach cultivation. A complete randomized design with three replications, was used in the experiment to implement a factorial design. Two soil textures of loamy and sandy treated with 1) without organic matter (C), 2) animal manure (M1 and M2), 3) medicinal plant residues including mallow (N1 and N2), 4) thyme (T1 and T2), and 5) nettle (H1 and H2) at 5% and 10% concentrations. Results indicated that loamy soil provided greater nitrogen (N) and iron (Fe) availability. The H2 treatment demonstrated remarkable efficacy in enhancing spinach growth traits in loamy soil, yielding the highest measurements for shoot fresh weight (2.70 g), root fresh weight (0.97 g), and leaf fresh weight (6.25 g). In contrast, the control treatment recorded significantly lower values of 0.28 g, 0.18 g, and 0.99 g for each respective trait. Furthermore, loamy soil exhibited the lowest pH at 6.9, alongside the highest bulk density of 0.63 g/cm³ and soil basal respiration rate of 116.43 mg CO₂-C g⁻¹ soil d⁻¹, particularly noted with the application of M2. Overall, loamy soil, combined with the H2 treatment, is recommended for optimal spinach cultivation, as it significantly improves growth traits and nutrient content, promoting sustainable agricultural practices.