Genotype, sulphur nutrition and soil type effects on growth and dry-matter production of spring onion

SummaryEffects of genotype, sulphur nutrition (0.0, 2.9, 5.8.kg S ha–1) and soil type (clay, sandy loam) on spring onion growth were investigated in glasshouse experiments. Leaf greenness, number of green leaves, leaf length, bulb diameter, total plant fresh weight, percentage dry matter (%DM) and total soluble solids content (TSS) varied significantly (P<0.05) among eight spring onion genotypes grown on sandy loam. Overall, A. cepa cultivars had more green leaves, taller plants and greater bulb diameter both with (5.8.kg S ha–1) and without S application than A. fistulosum cultivars. Deficiency symptoms of chlorosis, retarded growth and tip-burn were observed for plants not fertilized with S. S application differentially influenced TSS among genotypes. For example, S fertilization did not affect TSS of ‘Paris Silverskin’, but TSS was reduced by 30% in ‘Sydney Bunching’. Increased TSS was correlated with increasing %DM (r.=.0.77). On average, A. cepa cultivars were more responsive to applied S than A. fistulosum cultivars. More efficient S utilization resulted in greater increases in plant growth, bulb diameter and DM yield. For ‘White Lisbon’, increased S application from 0 to 2.9.kg ha–1 increased growth. There was no further increase when S was applied at 5.8.kg ha–1. TSS was reduced in response to added S. Growth of ‘White Lisbon’ was greater on clay than on sandy loam. However, TSS was not affected by soil type.