Mitigating asparagus decline through biosolarisation: a sustainable alternative to chemical soil fumigation

Abstract Asparagus decline syndrome (ADS) is a leading constraint in major producing regions and is closely associated with Fusarium -driven root and crown rot (RCR). We conducted a multi-year field trial in Aranjuez (Madrid, Spain) to compare pre-plant soil disinfestation strategies: chemical fumigation with dazomet, biosolarisation with hen-manure or Brassica-derived pellets, and an untreated control in a randomised complete block design (16 plots, four replicates). We quantified Fusarium inoculum in soil, plant growth, intercepted photosynthetically active radiation (PAR), radiation use efficiency (RUE), and spear yield. All disinfestation treatments produced an immediate reduction in soil Fusarium . Dazomet achieved the sharpest decline (total Fusarium to 1,031.9 ± 609.2 CFU g⁻ 1 ; F. oxysporum reduced by 98.3% to 47.2 ± 97.1 CFU g⁻ 1 ), while hen-manure and Brassica biosolarisation reduced F. oxysporum by 53% and 43%, respectively. In the establishment year, cumulative PAR intercepted by the asparagus canopy was highest under dazomet-treated plots (72.2 ± 16.1 MJ m⁻ 2 ), and by 2020 biosolarisation had matched dazomet (1,300–1,315 MJ m⁻ 2 ). By 2020, biosolarisation matched dazomet in terms of cumulative PAR intercepted by the asparagus canopy (1,300–1,315 MJ m⁻ 2 ). F. oxysporum inoculum was negatively correlated with final plant dry mass (R 2 = 0.684) and cumulative canopy-intercepted PAR (R 2 = 0.831). Across years, RUE did not differ significantly among treatments, indicating that biomass gains were primarily explained by greater radiation interception rather than by differences in radiation use efficiency. Early-season spear yield in 2019 correlated with prior-year dry biomass (R 2 = 0.67), and grade distribution shifted towards thicker spears (18–26 mm) under dazomet and hen-manure biosolarisation. Fumigation delivered only temporary gains, as Fusarium returned to high levels by year three, whereas biosolarisation sustained soil suppressiveness and crop vigour. Biosolarisation (especially with hen-manure pellets) emerges as a practical, lower-impact alternative to chemical fumigation for long-term ADS management.