Sulfur Nutrition Affects Garlic Bulb Yield and Allicin Concentration

Improving bulb yield and allicin content of garlic is important in meeting fresh and pharmaceutical market demands. Garlic plants have a high demand for sulfur (S) since allicin contains S atoms. Two experiments were conducted to identify the effect of S application rate on garlic yield and quality. In a field trial assessing six S application rates (0-150 kg S ha^-1), cultivar 'Glenlarge' produced the greatest bulb weight (~90 g) and allicin content (521 mg bulb^-1) with the application of 75 kg S ha^-1. In contrast, cultivar 'Southern Glen' showed no response in bulb weight or allicin. This was likely due to high soil background S concentrations masking treatment effects. Subsequently, a solution culture experiment with cv. 'Glenlarge' evaluated six S application rates (188 to 1504 mg S plant^-1, nominally equivalent to 25-200 kg S ha^-1). In solution culture, bulb weight and allicin concentration increased with S rate. Highest bulb weight (~53 g bulb^-1) and allicin concentration (~11 mg g^-1 DW) were recorded at an S application of 1504 mg S plant^-1. This is the first report to conclusively demonstrate the effect of S on yield and allicin in garlic grown in solution culture.