Effect of Deep Nitrogen Fertilizer Application on Grain Protein Content and Quality of Bread Wheat

In dry agricultural areas, plant uptake of nitrogen (N) stored in topsoil is limited as soil excessively dries up, especially in the late period of wheat growth. Deep N application is often suggested to ensure effectively use of water stored in the subsoil. This experiment was carried out in two different fields with different soils at Transitional Zone Agricultural Research Institute (TZARI) between 2012–2015 in the fallow-wheat rotation system. Efficiency of six different applications (1- deep Autumn 40 kg N ha⁻¹(A40), 2- deep Autumn 20 kg N ha⁻¹ (A20), 3-deep Spring 40 kg N ha⁻¹(S40), 4- deep Spring 20 kg N ha⁻¹(S20), 5- Traditional (T), 6- Control (C)) was investigated in Mufitbey and Bezostaja1 cultivars. The highest grain yield (4861 kg ha⁻¹) was obtained in deep application of 20 kg N ha⁻¹ in autumn, and the lowest grain yield (3969 kg ha⁻¹) was obtained in control. Also, the highest protein content of 12.65% was obtained with deep N applications of 20 kg N ha⁻¹ in autumn, while the lowest GPC (11.37%) was found in the control. Significant and high correlations occurred between nitrate content at 60 cm soil depth in the grain filling period and spike N uptake (<i>r</i> = 0.85, <i>P</i> &lt; .001), GPC (<i>r</i> = 0.84 <i>P</i> &lt; .001), farinograph number (<i>r</i> = 0.85, <i>P</i> &lt; .05), development time (<i>r</i> = 0.83 <i>P</i> &lt; .05) and yield (<i>r</i> = 0.96, <i>P</i> &lt; .001). Significant occurred between Bezostaja1 and Müfitbey in rheological (dough) properties. The data showed that climate and soil conditions should be taken into account in deep N application in dryland wheat farming.