Incorporation of Compost and Biochar Enhances Yield and Medicinal Compounds in Seeds of Water-stressed Trigonellia foenum-graecum L. Plants Cultivated in Saline Calcareous Soils

Abstract

Background The combination of compost and biochar (CB) plays an important role in soil restoration and mitigation strategies against drought stress in plants. In this study, the impact of CB was determined on the characteristics of saline calcareous soil and medicinal productivity of fenugreek plants (Trigonella foenum-graecum L.). The field trials examined CB rates (CB0, CB10 and CB20 corresponding to 0, 10, and 20 t ha‒1, respectively) under deficit irrigation (DI0%, DI20% and DI40% receiving 100, 80 and 60% ETc, respectively) conditions on growth, seed yield (SY), quality, and water productivity (WP) of fenugreek grown in saline calcareous. Results In general, DI negatively affected the morpho-physio-biochemical responses in plants cultivated in saline calcareous soils. However, amendments of CB10 or CB20 improved soil structure under DI conditions. This was evidenced by the decreased pH, ECe and bulk density but increased organic matter, macronutrient (N, P and K) availability, water retention, and total porosity; thus, maintaining better water and nutritional status. These soil modifications improved chlorophyll, tissue water contents, cell membrane stability, leaf PSII efficiency, and nutritional homeostasis in leaves of drought-stressed plants. This was also supported by increased osmolytes, non-enzymatic, and enzymatic activities under DI conditions. Regardless of DI regimes, SY was significantly improved by 40.0 and 102.5%, seed alkaloids by 87.0 and 39.1%, trigonelline content by 43.8 and 16.7% and WP by 40.9 and 104.5% in plants treated with CB10 and CB20, respectively. Conclusions Overall, application of organic amendments of CB can be a promising sustainable solution for improving saline calcareous soil properties, mitigating negative effects of DI stress, and enhancing crop productivity in arid and semi-arid agro-climates.