Effects of Nitrogen Fertilization Levels on the Growth, Bulb Quality, and Allicin Stability of Sliced ‘Hongsan’ Garlic during Storage

In this study, we investigated the effects of nitrogen fertilization on the growth, postharvest quality, and storage stability of Hongsan garlic.Growth, bulb size distribution, bulb quality, sliced garlic quality, and allicin content were evaluated under different nitrogen fertilization levels (0-3 N; 0, 240, 480, and 720 kg N•ha -1 , respectively).Nitrogen fertilization enhanced vegetative growth, including plant height, side shoot length, pseudostem length, and leaf number.At harvest, the proportion of small bulbs below 35 mm was highest in the non-fertilized control (61.6 ± 9.4%), whereas nitrogen fertilization markedly increased the proportion of 45-55 mm bulbs to 50.8-56.8%.Bulb weight also increased with nitrogen fertilization, reaching the highest value in the 2 N treatment (44.5 ± 7.6 g).However, clove firmness decreased as nitrogen fertilization increased, indicating that an excessive supply of nitrogen may negatively affect tissue stability.After four weeks at 20°C, sliced garlic firmness in the 2 N and 3 N treatments (9.5 ± 1.0 and 10.0 ± 1.7 N) was lower than that in the control (11.9 ± 0.5 N).Nitrogen fertilization also enhanced chlorophyll-based greenness on the upper clove surface and increased the browning index slightly during early storage.The initial allicin content was highest in the control [2,110.1 ± 54.1 µg•g -1 dry matter (DM)] and decreased with an increase in nitrogen fertilization, reaching 734.5 ± 49.9 µg•g -1 DM in the 3 N treatment.During storage, the allicin content decreased in all treatments but remained relatively high in the control.These results suggest that nitrogen fertilization improves growth and bulb development, whereas excessive application may reduce firmness and allicin stability.