Optimizing the Use of Locally Produced Slags as Amendments for Agro-Industrial Soils

Abstract

Circularization of nutrients is a key endeavor towards a sustainable intensification of agriculture, which reduces carbon dioxide emissions and prevent food scarcity. Steel slag is a by-product of the steel industry that contains an abundance of nutrients that could be repurposed to sustainably address some of the crops’ needs. During steel preparation, large amounts of carbon dioxide are released, and a range of inorganic (mineral) oxides are coproduced as slag. Herein, slag is explored as an amendment to sandy soils. First, the controlled release of nutrients from slag is thoroughly evaluated in various aqueous mixtures, including a range of organic acids. Organic acids, particularly acetic acid, associated with soil acidification are found to increase the release of nutrients, which are shown to substantially increase yields in plant assays. It was found that upon addition of acetic acid, the concentrations of iron, magnesium, and manganese increased from undetectable levels to 35.4, 20.1, and 9.6 ppm respectively. Tomato, typically growing in acidic soils, and salicornia, typically growing in alkali soils, are evaluated for their germination and seedling growth as a function of slag content. Low concentrations of slag have shown a positive effect on plant roots, particularly for cherry tomato, lateral roots number and tap root length increased by 88% and 44%, respectively when slag concentration increased from 0 to 0.1% slag (w/w). Similar effects were observed when growing arugula in the absence of soil (hydroponic growth). The starkest contrast were observed for Salicornia, where addition of slag increased the net weight by three fold in the seedling stage. This works highlights how emerging interactions between the agricultural and steel-making industries can optimize their carbon cycle, while improving nutrient cycling.

Date of Award	25 Jun 2024
Original language	American English
Supervisor	Blaise Tardy (Supervisor)