Synergistic Impact of Co-applied Micronized Sulfur and Nitrogen on Agronomical Traits of a Modern Spring Wheat Cultivars Grown in Alkaline Soil

Wheat (Triticum aestivum L.) uptakes only 40 to 60% of the soil available nitrogen. Sulfur deficiencies depress both nitrate uptake and nitrate reductase activity resulting in low nitrogen use efficiency. Soil and foliar supplied sulfur in combinations with foliar nitrogen were used on three of the modern and commercially grown wheat cultivars. The experiment was conducted in two consecutive growing seasons; 2017 and 2018 in a high pH soil, 8.55. Our results indicated that 714 kg ha-1 of pre-planting sulfur (SS) and spraying twice with 6.66% urea and 2.2% micronized sulfur (S1FS1N1) during stages 13 & 41 on Zadok`s scale, increased grain yield, total protein content, straw yield and plant height by 31.58, 26.09, 18.37 and 7.9% respectively. The results indicated a significant and positive impact sulfur-nitrogen combinations when applied on top of pre-planting applied sulfur. However, foliar sprayed sulfur had a more substantial effect on all traits, compared to the pre-planting sulfur or the foliar sprayed N, suggesting interference effect of the alkaline soil with the amount of sulfur recovered from the soil. When N and S foliar were applied simultaneously, a more substantial increase in grain yield, plant height, straw yield and total protein content was observed, suggesting a synergistic effect between these two elements. We attributed the positive effect of S1FS1N1 on improving photosynthates translocation from the sources to sinks. In addition to improving nitrogen use efficiency while reducing the plant content of NO−3 by optimizing the S/N ratio and reducing sulfur deficiency. Based on our results, we concluded that the foliar application of micronized S has the potential to improve the overall performance of wheat plants. Thus, we recommend enriching nitrogen and phosphate fertilizers with sulfur for alkaline soils.