Inclusion of Phaseolus vulgaris in fallow rice systems improves soil physical, physico-chemical and hydraulic properties under acidic sub-tropical conditions in Bangladesh

A range of cropping patterns is practiced in Bangladesh, which is likely to alter soil physical, physico-chemical, and hydraulic properties. To investigate the effects of different cropping patterns on soil physical, physico-chemical, and hydraulic properties, soil samples were collected from an 8-year long-term field experiment conducted in acidic soil during January–February 2024 at Sylhet, Bangladesh. The experiment followed a completely randomized design (CRD) and the tested patterns were: Fallow- Fallow–Rice (Transplanted (T.)-aman, Oryza sativa L.) (F1), Legume (Phaseolus vulgaris L.)–Fallow–Rice (T. aman) (F2), and Brinjal (Solanum melongena L.)–Fallow–Fallow (F3), which are the predominant cropping patterns and all maintained continuously for eight years. The results revealed that bulk density was significantly (p = 0.03) lower (1.11 g cm⁻³) in F2 compared with F1 (1.25 g cm⁻³) and F3 (1.26 g cm⁻³). Soil organic carbon differed significantly among cropping patterns (p < 0.0001), with the following order: F2 (2.29%) > F1 (1.60%) > F3 (1.31%). Saturated hydraulic conductivity (p = 0.0003) and sorptivity (p = 0.0002) were higher in F2 (0.057 mm s⁻¹ and 2.14 mm s⁰·⁵, respectively) than in F1 (0.003 mm s⁻¹ and 0.42 mm s⁰·⁵, respectively) or F3 (0.005 mm s⁻¹ and 0.69 mm s⁰·⁵, respectively). Structural stability index (p = 0.03) reached optimal levels in F2 (9.84), near-optimal in F1 (8.57), and critical in F3 (7.00). Overall, the legume-based (F2) cropping pattern improved soil physical, physic-chemical and hydraulic properties, indicating enhanced soil aggregation, porosity, and water infiltration. Therefore, replacing fallow periods with legumes can enhance soil health and promote sustainable management of acidic soils in sub-tropical conditions. Long-term legume-based cropping pattern improves soil physical and hydraulic properties in acidic soils of Sylhet. Bulk density decreases by approximately 11–12% and increases soil organic carbon approximately 43–73% under legume rotations compared with fallow-dominated systems. Saturated hydraulic conductivity is 11–19 times greater and sorptivity is 3–5 times greater under legume-inclusion cropping patterns, indicating improved water infiltration. Structural stability index reaches optimal levels in legume-based rotations, highlighting the greater structural stability.