Effect of Mineral Fertilizers On Irrigated Winter Wheat Yield and Grain Protein Composition.

A two year field experiment was conducted in Moldova to study the effect of mineral fertilizers (Control – No fertilizers, N90K60, P90K60, N90P90, N90P90K60, N90P90K90, N90P120K60, N90P180K60, N120P90K60, and N180P90K60) on irrigated winter wheat (cv. Kavkaz 1) yield and grain protein composition. The soil at the experimental site was a chernozem, containing humus  3.73 %, total nitrogen 0.2%, plant-available P₂O₅ and K₂O 10.8 and 25 mg/100 g respectively,  extractable cations Ca²⁺ and Mg²⁺  27.2 and 2.4 meq/100 g respectively, with pH_H20 value of 7.2 at the 0-10 cm soil depth. The results revealed that mineral fertilizers significantly increased winter wheat grain yield compared to the control. The highest wheat grain yield gain, 1.44 t ha^-1 (p=.000027, at α=.05, by LSD), was achieved when the plants were fertilized with N120P90K60 kg ha^-1, but not all the grain yield values were significantly different between the fertilizer treatments. The grain yield did not significantly respond to increasing rates of nitrogen or phosphorus at the 90 to 180 kg ha^-1 treatment. The ranges of grain protein value were 10.6–14.4% and its concentration increased linearly with the nitrogen fertilizer rate. The non-gluten proteins albumins and globulins content ranged from 2.74-3.19% and were influenced slightly, whereas amounts of gluten proteins gliadins and glutenins were 3.42–5.53% and 3.31-4.90% and increased on average by 2.11 and 1.22% respectively in the wholemeal flour treatment (N180P90K60) compared to the control. Similarly, the gliadins to glutenins ratio increased from 0.93 to 1.13.  Wet gluten comprised 20-25% of the wholemeal flour and increased on average by 11.5 % (N180P90K60) compared to the control. There was not a large difference in the amount of residue proteins in the wheat wholemeal flour, which ranged from 0.54 to 0.63%. Hence, the use of mineral fertilizers is essential to increasing irrigated winter wheat grain yield and grain storage protein content on chernozem soil.