Assessment of soil health in indigo cultivated land at Northern Bangladesh

<table style="width: 98.9%; border-collapse: collapse;"> <tbody> <tr style=""> <td style="width: 70.94%; padding: 0in 5.4pt 0in 5.4pt;"> <p><span>Indigo (<em>Indigofera tinctoria</em> L.), a nitrogen-fixing legume, has re-emerged in Northern Bangladesh as a sustainable cash crop with agronomic, ecological, and socio-economic benefits. However, its long-term effects on soil health remain poorly quantified. This study assessed key physicochemical and biological properties like pH, soil organic carbon (SOC), total nitrogen (TN), available phosphorus (P) and sulphur (S), and microbial biomass carbon (MBC) across eight indigo cultivation sites representing diverse soils and management histories. Results revealed substantial spatial heterogeneity, with pH ranging from 5.09 to 6.31, SOC from 0.57% to 2.24%, and TN from 0.08% to 0.17% (p < 0.001 for SOC and TN). The majority of sites (62.5%) exhibited SOC < 1.0%, indicating organic matter depletion, while Leavens Blue emerged as a fertility hotspot with SOC levels four times greater than in the most degraded site. Available P (14.85–33.69 ppm) and S (0.14–12.00 ppm) showed high within-site variability without significant regional differences, and MBC ranged from 187.29 to 637.20 mg kg⁻¹, reflecting sensitivity to micro-environmental conditions. These findings highlight that while indigo can sustain soil fertility under appropriate management, notable differences between sites demand tailored interventions particularly pH correction and organic matter enhancement to optimize productivity and ecological resilience. This work provides the first comprehensive evidence base for developing region-specific soil management strategies in support of indigo’s role in sustainable agriculture and rural livelihoods in Bangladesh.</span></p> </td> </tr> </tbody> </table>