Cumulative effects of biochar application on faba bean productivity and nodulation in arid soil over three growing seasons

Abstract

Background: Faba beans (Vicia faba L) are major grain legumes used worldwide as a source of micronutrients and plant-based proteins. Although biochar soil physicochemical and biological properties, its long-term effects on faba bean yield and nodulation under field conditions remain poorly understood. Aim: This study examined the residual impacts of a single biochar application made three years prior on faba bean growth, yield, root development, and nodulation. Methods: Three treatments were arranged in a randomized complete block design: control (T1), 5 t ha⁻¹ (T2), and 10 t ha⁻¹ (T3). Plant height and branch number were measured at different phenological stages, and root length, nodule number, and final seed yield were recorded at harvest. Data were analyzed using analysis of variance with post hoc comparisons (P < 0.05). Results: Biochar significantly improved the growth and yield parameters (P < 0.001). Seed yield increased by 1.96-fold and 2.25-fold under T2 and T3, respectively, compared with T1. The root length increased by 67.5% under T2 and 49.1% under T3, whereas the nodule number increased by 4.38-fold under T2 and 1.85-fold under T3 relative to the control. Root length and nodulation peaked at T2, with T3 producing the highest final seed yield. Conclusion: The cumulative effects of biochar remained detectable after three growing seasons. T3 is recommended for maximizing grain yield, whereas T2 is more effective for enhancing root development and nodulation, suggesting that specific agronomic priorities should be considered when selecting a treatment.