Morphological and nutritional responses of sorghum to variable irrigation levels and nitrogen doses

This study aimed to determine the effects of different irrigation levels (50%, 75%, and 100% of ETo values calculated using evaporation from Class-A pan) and nitrogen doses (0, 90, 180, and 270 kg ha ⁻ ¹) on yield, yield components, and the nutritional properties of sorghum grains. According to the research results, increasing irrigation and nitrogen fertilization levels enhanced plant height, thousand-grain weight, grain number per panicle, grain weight per panicle, and grain yield. The highest grain yield (7120 kg ha ⁻ ¹) was obtained with 100% irrigation and 180 kg ha ⁻ ¹ N application. While increasing irrigation levels increased oil content, higher nitrogen doses caused a decrease for it. The highest oil content (6.64%) was recorded with 100% irrigation and 0 kg ha ⁻ ¹ N application. Protein content increased with irrigation and nitrogen applications, reaching the highest level (11.85%) with 100% irrigation and 270 kg ha ⁻ ¹ N application. Higher irrigation levels also increased total starch and phytic acid content. Among nitrogen applications, the dose of 270 kg ha ⁻ ¹ resulted in the maximum total starch (77.29%) and phytic acid content (1.83%). The ratio of resistant starch (RS) was found to be high at 50% irrigation with low nitrogen doses, indicating an inverse relationship with the total starch content. Both irrigation and nitrogen applications significantly affected the ratios of oleic and linoleic acids. Specifically, increased irrigation raised the linoleic acid content, while nitrogen applications enhanced the oleic acid content. Additionally, as irrigation levels increased, the contents of potassium (K), magnesium (Mg), iron (Fe), phosphorus (P), and zinc (Zn) also increased. Conversely, the levels of calcium (Ca) and manganese (Mn) decreased. Generally, higher nitrogen doses resulted in increased mineral content, with the highest levels of magnesium, iron, and zinc observed at nitrogen doses between 180 and 270 kg ha ⁻ ¹. According to the research results, the most suitable irrigation level for optimizing high yield and grain nutritional properties was determined to be 100%, with a nitrogen dose of 180-270 kg ha ⁻ ¹. These findings will contribute to future studies on different sorghum varieties under varying climate and soil conditions.