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This study aims at assessing the effect of limestone mining by-product from the Irati Formation on soil calcium, magnesium, and sulfur contents, as well as their accumulation in the onion biomass. The study was carried out in a greenhouse. A Eutrophic Haplic Planosol (SXe) and a Eutrophic Yellow Argisol (PAe) soil were used. The treatments included the control, limestone by-product, dolomitic limestone, calcium (Ca) + magnesium (Mg) carbonates, and Ca + Mg carbonates + gypsum. Onions were grown in pots containing 10 dm3 of soil kept at a moisture level close to the field capacity. The onion biomass harvest (bulb + leaves) was performed 77 days after transplanting. Afterwards, the soil macronutrient content and the dry onion biomass were determined, as well as its production. The by-product application increased Mg2+ content in both soils (+74% in SXe and + 182% in PAe) and Ca2+ and sulfate (S-SO42-) contents, respectively, in the PAe (+62%) and SXe (+124%). There was an increase in S accumulation due to the onion biomass cultivated in both soils (about 85%). Regarding Ca and Mg accumulations, no difference was observed in the by-product treatment when compared to the control. Therefore, it is possible to infer that the limestone mining by-product from the Irati Formation is potentially useful as a source of secondary macronutrients and proves to be a clean environmental solution for soil fertilization, increasing the sustainability of the local production system. [ABSTRACT FROM AUTHOR]

The nutrition of onion grown in a no-tillage system with compost requires research to provide alternatives to mineral fertilizers. Our objective was to evaluate the effect of compost rates on the nutrient content in the tissue of onion grown in a no-tillage system. We conducted a field experiment with the following treatments: 0, 10, 20, 30, and 60 Mg ha−1 of compost and mineral fertilization. We applied these treatments in 2018, 2019, and 2020 for onion cultivation. We used a 3 × 6 factorial scheme (year x treatment) and four replications. We evaluated the bulbs and whole plant nutrient contents of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, and B. In 2020, nutrient content in the bulb from 10 Mg ha−1 of compost was similar to the mineral fertilizer's treatment. Therefore, compost can replace mineral fertilizers to supply nutrients to the onion. However, the continuous application of compost requires soil monitoring due to nutrient accumulation. [ABSTRACT FROM AUTHOR]