Sulfur and nitrogen fertilizer effects on wheat. I. Concentrations of sulfur and nitrogen and the nitrogen to sulfur ratio in grain, in relation to the yield response

Grain samples from a factorial (5 sulfur x 3 nitrogen treatments) field experiment with Olympic wheat, which showed yield responses to both factors, were analysed for total sulfur and nitrogen. Sulfur application increased the grain sulfur concentration more with high than with low nitrogen treatment, but had only small effects on the nitrogen concentration in grain. Nitrogen application increased the grain sulfur concentration at high but not low sulfur and increased grain nitrogen concentration at all sulfur treatment levels. The critical grain sulfur value for yield was 0.12% in treatments adequately supplied with nitrogen, but plots with low nitrogen (sulfur-unresponsive) also had grain sulfur values below 0.12 %. Grain from sulfur-responsive plants could be distinguished from grain from unresponsive plants because the former had less than 0.12% sulfur and nitrogen/sulfur ratios wider than 17/1. Results from a glasshouse experiment with three cultivars were consistent with this. The findings suggest that seed analysis may be a useful method for diagnosis of the sulfur status of cereal crops.