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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]

The study was aimed to evaluate the effect of successive applications of increasing biochar rates along with other mineral fertilizers and poultry manure on onion nutrition and yield. The experiment consisted of 2 (agricultural year) × 11 (treatments) factorial combinations over two cropping years (2017 and 2018). Thus, 11 treatments were tested as follows: C = control; MF = mineral fertilizer; PM = poultry manure; B1+ MF = 1 Mg ha−1 of biochar+MF; B1+ PM = 1 Mg ha−1 of biochar+PM; B2+ MF = 2 Mg ha−1 of biochar+MF; B2+ PM = 2 Mg ha−1 of biochar+PM; B4+ MF = 4 Mg ha−1 of biochar+MF; B4+ PM = 4 Mg ha−1 of biochar+PM; B10+ MF = 10 Mg ha−1 of biochar+MF; B10+ PM = 10 Mg ha−1 of biochar+PM. The highest onion yield (39.9 Mg ha−1) was obtained in 2017 with the biochar rate of 5.9 Mg ha−1 while an increase of 308 kg ha−1 in onion yield was found for each Mg ha−1 of biochar added to soil in 2018. The use of biochar combined with mineral fertilizers increased onion yield; and the use of biochar combined with poultry manure improved soil fertility status. [ABSTRACT FROM AUTHOR]

In this research experiment, two commercial onion cultivars (Allium cepa L., cvs. Dorrcheh and Cebolla Valenciana) were grown in sand culture and exposed to two levels of selenium (Se) (0 and 25 µM) and two levels of sulfate (1 and 3 mM). According to the results obtained, addition of 25 µM Se in combination with 3 mM sulfate was not only effective in significant increase of onion bulb yield, but it significantly increased Se concentration of bulb. By considering the average consumption of onion in central Iran, the daily intake of Se via consumption of Se-biofortified onion is estimated to be 68.4-77.2 µg in spring and summer and 72.6-117.1 µg in fall and winter. These amounts of daily intakes of Se is higher than the sufficient levels of Se recommended by world health organization (WHO) but less than the maximum tolerable level of Se (400 µg Se per day) for human. [ABSTRACT FROM AUTHOR]