Restoring Soil Fertility in Phosphate Mining Sites Using Engineered Anthroposols and Local Tree Species

Phosphate mining generates vast quantities of phosphogypsum and sludge, leaving lands nutrient-poor and erosion-prone. Conventional rehabilitation often fails on these substrates, necessitating circular, waste-to-resource solutions. This study presents a cost-effective method to create fertile anthroposols from industrial by-products, enabling ecological restoration.At Morocco’s Ben Guerir mine, a randomized block design tested six local, drought-resistant tree species on anthroposol, a 50 cm layer composed of 65% phosphogypsum, 30% phosphate sludge, and 5% sewage sludge. Seedlings were spaced 6 meters apart, with drip irrigation reserved for extreme drought. No external fertilizers were applied. After two years, all species outperformed controls on natural soil. Fruit trees (carob, olive, argan) and forest trees (false pepper, eucalyptus, pistachio) exhibited robust growth, with forest species reaching up to 268 cm. Soil analysis revealed decreased P, K, and Mg due to plant uptake, while exchangeable Ca increased, raising pH and nutrient availability. Heavy metal levels remained stable or declined, with leaf concentrations below toxicity thresholds (BCF < 1), confirming safe phytostabilization. Argan and false pepper excelled in Cd, Cr, Cu, and Ni uptake, while eucalyptus and carob proved effective for erosion control. Strong correlations between growth and foliar N, K, and Ca underscore the importance of balanced nutrients in anthroposols. This approach delivers three key benefits: restoring degraded lands, immobilizing heavy metals, and fostering sustainable vegetation. Policy recommendations include integrating anthroposol technology into mine closure plans and prioritizing local species for phytostabilization.