Moderate Biochar–Compost Mixture Is More Effective in Improving Biomass, Nutrient Fluxes, and Photosynthetic Outputs for Sustainable Land Restoration and Soil Fertility

ABSTRACT

Soil nutrient depletion severely constrains crop productivity in degraded and saline environments. Strategies such as biochar–compost integration could be useful for sustainable agriculture and land restoration on a global scale. This study evaluated the effects of biochar (1% Bc), compost (1% Co), and their blends (0.5% Bc + 0.5% Co and 1% Bc + 1% Co) on soil properties, growth, physiology and nutrient balance of the halophytic fodder crop P. antidotale under controlled greenhouse conditions. The 0.5% Bc + 0.5% Co treatment increased total plant biomass by 68%, net photosynthesis by 68% and stomatal conductance by 90% compared to the control while soil water holding capacity and CO ₂ flux were also significantly enhanced. Sole biochar improved leaf water‐use efficiency (18%) and maximized K ⁺ /Na ⁺ ratios across plant organs, indicating improved ionic balance under nutrient‐poor soil conditions. Biochar–compost blends significantly increased leaf nitrogen (25%) and carbon (4%) concentrations relative to untreated plants with the lower mixture ratio consistently outperforming higher amendment levels. These responses are likely mediated through improved soil water retention, nutrient availability and rhizosphere functioning. Overall, integrating moderate biochar–compost amendments offers an effective and scalable strategy for enhancing halophyte productivity and soil quality in degraded agroecosystems.