Effects of liquid nitrogen applications during the heading stage on grain yield and bulgur quality of durum wheat varieties

The aim of this research was to determine the effects of foliar fertilization with urea nitrogen, at a low urea concentration, on durum wheat yield, yield components, and bulgur quality when applied in addition to traditional fertilization at different doses and times. The trials were carried out under irrigated conditions on farmer's land in Antalya, Korkuteli, Garipçe village during the 2020-21 and 2021-22 growing seasons. The Kızıltan-91 and Mirzabey 2000 varieties were used in the experiments. The study was conducted with three replications in a factorial trial design in randomized blocks. Foliar urea solution was applied with a backpack sprayer at four different doses: 200 ppm, 400 ppm, 600 ppm, and 800 ppm, and at three different stages: the beginning of flowering, mid-flowering, and after flowering. For each variety, seeds were sown at a density of 400 seeds per square meter using a seed drill, with row spacing of 14 cm and a total of 8 rows. The plot cultivation area measured 1.12 × 5 m (5.6 square meters). 30 kg/da of diammonium phosphate (DAP) was applied to the soil, and 10 kg/da of urea was applied twice—once before tillering and once before germination. Weeds were controlled across the entire trial area using a 2-4-D ester herbicide when weeds had 3–5 leaves. The experiments were irrigated four times at a rate of 100 mm/m²—during sowing, tillering, and heading stages, as well as for germination and emergence, as recommended for wheat cultivation. Grain yield per plot, hectoliter weight, thousand-grain weight, grain moisture, vitreous grain ratio, and sieve analysis were measured. Sedimentation tests, gluten index, wet gluten content, protein content, and semolina color analyses were performed on grains that were hand-harvested and threshed using a laboratory-type threshing machine. Bulgur yield and color values were determined by processing wheat samples into bulgur. It was found that foliar application of liquid urea increased yield per decare and did not significantly change average hectoliter weight or thousand-grain weight. In studies evaluating the vitreous grain ratio, Kızıltan-91 and Mirzabey 2000 varieties exhibited ratios ranging from 78% to 80%. Average b color values, measured as yellow color indicators, ranged from 21.1 to 26.1 and were significantly affected by both the liquid urea application dose and application timing. Protein content ranged from 12.3% to 16.1%, and it was significantly influenced by liquid urea application dose and timing. Average sedimentation values were significantly affected by genotype, flowering stage, and urea dose. The highest average wet gluten content (50.7%) was obtained from the application of 800 ppm liquid urea at the end of flowering for the Kızıltan-91 variety, while the lowest (18.6%) was observed in the control plot of the same variety. The highest gluten index (58%) was recorded for the application of 200 ppm liquid urea at mid-flowering in Kızıltan-91, while the lowest gluten index (19%) was from the control plot of Kızıltan-91. The highest bulgur yield (64%) was obtained from wheat treated with 200 ppm liquid urea applied at the end of flowering for the Mirzabey 2000 variety, while the lowest yield (36%) was recorded for wheat treated with 200 ppm liquid urea at the beginning of flowering in the same variety. For bulgur b color values, the highest (28) was observed in wheat treated with 400 ppm liquid urea during mid-flowering for Mirzabey 2000, while the lowest (22.6) was from wheat treated with 200 ppm urea at the start of flowering for Kızıltan-91.