Optimalization of Nitrogen and Sulfur Fertilization of Hypoallergenic Winter Wheat Lines

This study evaluated the response of two winter wheat lines: hypoallergenic wasko.gl− and control line wasko.gl+ to nitrogen (N) and sulfur (S) fertilization under field conditions in southern Poland during 2019–2021. A split-split-plot design with six N doses (0–120 kg ha−1) and three S doses (0, 20, 40 kg ha−1) was applied to assess grain yield, nitrogen agronomic efficiency (NAE), vegetation indices (LAI, NDVI), and grain protein content. Grain yields ranged from 3.92 to 6.08 Mg ha−1, with the hypoallergenic line producing on average 16.6% more than the control one. Nitrogen fertilization significantly increased yields up to 80–100 kg N ha−1, while sulfur application showed no consistent yield effect. The highest NAE was achieved at 80 kg N ha−1, reaching 13.7 kg grain kg−1 N for hypoallergenic and 19.6 kg grain kg−1 N for the control wheat line. Remote sensing indices correlated with fertilization intensity; LAI and NDVI increased up to 80–100 kg N ha−1, with optimal values differing between lines, confirming distinct nitrogen-use efficiencies. Grain protein content increased systematically with higher N inputs, exceeding 145.6 g kg−1 DM at 120 kg N ha−1; sulfur fertilization modified protein levels, with the optimal dose being 20 kg S ha−1 for the hypoallergenic line and 40 kg S ha−1 for the allergenic line. Results demonstrate that nitrogen supply strongly influences yield and quality traits, whereas sulfur plays a secondary role, particularly in modifying protein content in grains. Differences in genotype responses to fertilization emphasize the importance of taking an individualized approach to nitrogen and sulfur fertilization strategies, which are tailored to specific lines of wheat. This optimizes fertilization, yield, and quality, while maintaining environmental sustainability.