DOES NITROGEN AND SULFUR FERTILIZATION AFFECT SUNFLOWER GRAIN YIELD AND QUALITY?

Abstract

Agricultural intensification decreased soil organic matter levels. Therefore, nitrogen (N) and sulfur (S) deficiencies are becoming more frequent, possibly limiting sunflower (Helianthus annuus L.) grain yield and quality. The aim of this work was to evaluate the effect of N and S fertilization on: 1) yield and its components, 2) protein and oil concentration, and 3) fatty acid concentration in sunflower grains. Six field experiments were conducted during 2018-2019 with high oleic hybrids (crop season 1) and 2019-2020 growing season with conventional hybrids (crop season 2). Two N rates (40 and 80 kg N ha^-1) without S, and with S (20 or 40 kg S ha^-1, depending on the crop season), plus an absolute control (without N and S) were evaluated.  N fertilization increased significantly sunflower yield and grain number only for season 1, while S did not affect these variables for none of the analyzed seasons. Grain quality was not modified by S addition, while N only increased the protein content at a high rate (80 kg N ha^-1) only for season 1. In summary, for the southeastern Buenos Aires conditions, N fertilization increased sunflower grain yield and protein content, while S did not affect yield or grain quality.