Barley Grain Nitrogen Concentration as Affected by Drought and Nitrogen Fertilizer

High grain yield and acceptable grain quality are required for profitable production of barley crops. Grain nitrogen concentration (N%) is a major determinant of grain quality in cereal crops. The aim of this study was to survey the effects of applied water and nitrogen fertilizer on grain nitrogen concentration of barley (cv. Reyhaneh 0-3). This experiment was performed with 5 irrigation levels (first water, 0, 50, 75, and 100 % of water requirement named as I0, I1, I2, I3 and I4, respectively) as the main plot and 4 nitrogen fertilizer levels (0, 70, 140 and 210 kg N ha-1, named as N1, N2, N3 and N4) as the subplots using spilt plot design with 3 replications. The grain nitrogen concentration was enhanced by increasing applied nitrogen fertilizer. Grain nitrogen concentration of N2, N3 and N4 were increased by 21, 33 and 56 percent, respectively, compared with that at N1. Results showed that enhancing applied water in all nitrogen treatments resulted in the decrease of grain nitrogen concentration, whereas increasing applied water from I2 to I4 did not change grain nitrogen concentration, significantly. The latter occurred due to nitrogen leaching in high irrigation levels and therefore more nitrogen moved to lower soil layers and became inaccessible to the root; and resultantly to the crop. Furthermore, in deficit irrigation treatments (such as I0 and I1), apart from the negative effect of decreasing matric potential, the increase in nitrogen concentration lead to a decrease in osmotic potential, total water potential, root water and nitrogen uptake, and finally crop production.