Recycling Electric Arc Furnace Slag into Fertilizer: Effects of “Waste Product” on Growth and Physiology of the Common Bean (Phaseolus vulgaris L.)

The aim of this study was to investigate if electric arc furnace (EAF) slag generated during steel production could have an application as a soil enhancer in agriculture. For that purpose, a greenhouse experiment was conducted on common beans (Phaseolus vulgaris) cultivated in soil enriched with EAF slag (at 1% and 2% level), synthetic fertilizer (NPK), combined EAF slag and synthetic fertilizer, or in control (untreated) soil. The beans were exposed to test soils until maturity (for 8 weeks). Following that period, physico-chemical properties of the soils, as well as nutrient status, growth, photosynthetic and oxidative stress parameters of bean plants were determined. EAF slag improved the mineral status of the soil and significantly increased Fe, Mg, N, P and K in different bean plant organs. EAF slag and/or NPK increased plant height. EAF slag, especially at lower levels, positively affected dry weight of leaf and seed. Soil supplementation with a lower level of EAF slag, as well as with a combination of EAF slag and NPK, led to significant improvement in gas exchange parameters (net photosynthetic rate, intercellular CO₂ concentration and stomatal conductance) and nitrate reductase activity, indicating a positive influence on bean plants. Potential phytotoxicity of EAF slag was not detected, as evidenced by the oxidative stress parameters. Thus, EAF slag applied at a low level shows promising potential as an efficient soil enhancer, and as a valuable source of nutrients essential to plants, with an equal or even better performance compared to synthetic fertilizer.