Remediation of Ni toxicity by liming - field validation

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Remediation of soils contaminated with metals may be achieved through application of agricultural lime, which is expected to reduce plant-available metal by increasing soil pH. However, raising the pH can potentially reduce the bioavailability of essential elements, which may negatively impact crop yields. The present study will revisit a set of agricultural fields in Port Colborne (ON) elevated in Ni, Cu, Co, and As, which were amended with dolomitic lime at either 10 or 50 t/ha a decade ago and yields of oat and soybean were determined in three subsequent years. These fields will be replanted with soybean to evaluate the long-term efficacy of liming as a remediation strategy (Objective 1). These data will be compared to agronomic yield of soybean in fields more recently amended with 88 t/ha of lime (Objective 2). The effect of calcitic versus dolomitic lime on agronomic yield of soybean will be compared in two sets of fields. For both fields, agronomic response and tissue accumulation of Ni will be related to total soil Ni, soil chemistry parameters known to modify bioavailability, soil solution Ni and plant available Ni (Objective 3). An alternate to liming as a remediation strategy is reducing the Ni concentration in surface soils through phytoremediation. Using a Ni hyperaccumulator (Alyssum murale), pot and in situ field studies will provide data of soil to plant transfer which will be used to populate STELLA® models, which allow simulation of a system over time. The outcome will be estimates of the half-life of Ni in surface soils under a number of different scenarios (Objective 4). Finally, the potential for dilution of surface contamination by 'deep tilling' versus the expected loss in crop productivity by bringing less fertile B horizon soils into the root zone, will be evaluated (Objective 5). Integration of these studies will enable a decision support system for soil remediation strategies for this site, which can also be applied to other metal-contaminated areas in Canada (e.g. brownfields). The new knowledge will support the Canadian mining industry in being competitive worldwide by developing and demonstrating practical agronomic interventions suitable for large-scale use, rather than technology-intensive processes.