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Nickel-enriched soil acidity amendments (SAA) may be advantageous for neutralizing acidity and providing safe/uniform distribution of Ni in soils. We evaluated the short-term effects of Ni application on field-grown soybean yield, growth, and soil chemical attributes using three sources of SAA, two enriched with Ni (Ni-rich mining by-product and Ni-salt) and a commercial SAA. The tested Ni-enriched sources were effective in providing Ni to the soil at safe levels, neutralizing acidity and increasing base saturation. A one-time Ni application resulted in optimal Ni levels in the first cropping season, enhancing grain yield by up to 658 kg ha−1 and improving nitrogen metabolism in soybean. A low residual effect of Ni was observed in the second year, with soil available Ni and plant Ni concentrations decreasing to sub-optimal levels and yield gains not being observed. In conclusion, the application of Ni-enriched SAA is a sustainable technology for agriculture, optimizing soil management practices. The SAA derived from by-products has benefits to the mining sector, meeting the 'Ensure Sustainable Consumption and Production Patterns' (SDG 12). Our findings suggest that this micronutrient may require a year-to-year adjustment via Ni-fertilization and the total Ni concentration in the soil should be monitored over the cropping seasons. [ABSTRACT FROM AUTHOR]

Abstract Fly and bottom ashes - by-products of petroleum coke combustion - contain important plant nutrients (e.g., Ca, S) and may be used as soil acidity amendments, yet their metals content might be a concern. Finding innovative alternatives for the beneficial use of such by-products is key for assuring their environmental sustainability. In this study, we first carried out a comprehensive characterization of fly and bottom ashes, i.e., physical, chemical, mineralogical, and structural analyzes. Next, we created a new product based on these ashes to meet the demand of the Brazilian legislation. To test the agronomic efficiency of the product and the environmental implications of its agricultural use, greenhouse experiments were performed with two Oxisols, cultivated with maize and soybean. The treatments consisted on the application of two doses of different products, aiming to increase soil base saturation to 50% and 70%, and three sources: 1) a blend of fly and bottom ashes with commercial limestone (blended limestone, BL); 2) a positive control, commercial limestone enriched with Ni and S (enriched limestone, EL); and, 3) a negative control (commercial limestone, CL). The BL was efficient for soil acidity correction, providing Ca, Mg, S, and Ni to maize and soybean plants. Plant dry weight did not change following the application of the product, yet the BL was effective as a Ni-fertilizer, since it was able to increase soil-Ni up to 5-fold, as well as Ni content in maize and in soybean leaves by 5- and 4-fold, respectively, positively affecting N metabolism. Our findings revealed that, while improving many soil attributes, the BL is a viable and sustainable technology for the use of petroleum coke combustion ashes in agriculture, working as a Ni-fertilizer to plants, which meets a current market demand for this micronutrient. [ABSTRACT FROM AUTHOR]