Fertilizer Efficiency and Risk Assessment of the Utilization of AOD Slag as a Mineral Fertilizer for Alfalfa (Medicago sativa L.) and Perennial Ryegrass (Lolium perenne L.) Planting

Argon oxygen decarburization (AOD) slag is the by-product of the stainless steel refining process, which has caused considerable environmental stress. In this work, the utilization of AOD slag as mineral fertilizer for alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) planting were investigated by pot experiments. The morpho-physiological parameters of biomass, plant height, root morphology and the biochemical parameters of malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, peroxidase (POD) activity, and chlorophyll were measured. The accumulation of chromium in plants was also determined for an environmental safety perspective. It was found that low rates (≤0.5 wt.% for alfalfa and ≤2 wt.% for perennial ryegrass) of AOD slag fertilization are beneficial to the growth of these two plants. However, the soil enrichment with higher AOD slag amounts resulted in the reduction of biomass, plant height, and root growth. Compared with the alfalfa, the perennial ryegrass showed higher tolerance for AOD slag fertilization. The toxicity of the utilization of AOD slag as mineral fertilizer for perennial ryegrass planting is slight. Health risks induced by the consumption of the alfalfa grown on the soil with high AOD slag rates (≥8 wt.%) were detected.