Field assessment of organic amendments and spring barley to phytomanage a Cu/PAH-contaminated soil

The INTENSE project, supported by the EU Era-Net Facce Surplus, aimed at increasing crop production on marginal land, including those with contaminated soils. A field trial was set up at a former wood preservation site to phytomanage a Cu/PAH-contaminated sandy soil. The novelty was to assess the influence of five organic amendments differing in their composition and production process, i.e. solid fractions before and after biodigestion of pig manure, compost and compost pellets (produced from spent mushroom substrate, biogas digestate and straw), and greenwaste compost, on Cu availability, soil properties, nutrient supply, and plant growth. Organic amendments were incorporated into the soil at 2.3% and 5% soil w/w. Total soil Cu varied from 179 to 1520 mg kg^-1, and 1 M NH₄NO₃-extractable soil Cu ranged from 4.7 to 104 mg kg^-1 across the 25 plots. Spring barley (Hordeum vulgare cv. Ella) was cultivated in plots. Changes in physico-chemical soil properties, shoot DW yield, shoot ionome, and shoot Cu uptake depending on extractable soil Cu and the soil treatments are reported. Shoot Cu concentration varied from 45 ± 24 to 140 ± 193 mg kg DW^-1 and generally increased with extractable soil Cu. Shoot DW yield, shoot Cu concentration, and shoot Cu uptake of barley plants did not significantly differ across the soil treatments in year 1. Based on soil and plant parameters, the effects of the compost and pig manure treatments were globally discriminated from those of the untreated, greenwaste compost and digested pig manure treatments. Compost and its pellets at the 5% addition rate promoted soil functions related to primary production, water purification, and soil fertility, and the soil quality index.