Study on nitrogen rate and time application effects in nitrogen use efficiency and different dryland wheat genotypes quality and quantityý.

In order to study nitrogen rates and nitrogen application time's effects on nitrogen requirement, nitrogen use efficiency (NUE) and dryland wheat genotypes quality and quantity, this project carried out in RCBD split split plot with two nitrogen time application (Fall, 1/2 fall+ 1/2 spring and 2/3 fall+1/3 spring ) in main plot, nitrogen rates (0, 30, 60, 90 and 120 kg/ha from urea fertilizer) in sub plot and five drylan wheat genotypes (Azar 2, Sardari, Homa, Sardari 101 and Rasad) in sub-sub plot whit 3 replications and three cropping years (2006-2009) in Maragheh Dryland Agricultural Research Institute (DARI). The results showed that nitrogen application rates significantly increased grain, biological and straw yields, harvest index (H.I), degree productivity (DP), number of spikes per m2, plant height, head length, number of fertile tillers, number of seeds per head, plant weight, root fresh weight, root volume, and number of nodal roots. Path analysis results showed that the most positive and significant effect on grain yield had root fresh weight, root volume and number of nodal roots respectively. Most agronomy nitrogen use efficiency obtained from 30 kg N/ha and with increasing of nitrogen rates, nitrogen use efficiency significantly decreased in a linear. Dryland wheat mean nitrogen requirement in order to achieve 90% grain yield determined 50 kg of nitrogen per ha (100 kg urea per ha) with climate constraints such as cold early spring and drought stress. With GGE Biplot analysis method suitable nitrogen application time for Azar 2 and Homa cultivars were 2/3 split + 1/3 spring and for Sardari cultivar was fall application in autumn by placement method. Also the results showed that application of nitrogen rates increased wheat grain protein concentration significantly in a linear. In the nitrogen treatment ranges (0 to 120 kg N ha) with application of one nitrogen per ha, grain protein concentration increased 0.025 percentage. The highest and lowest grain protein concentration obtained 11.6% and 104 % from Rasad (class A) Sardari 101 (class B) cultivars respectively. It can be concluded that nitrogen application rates and times affected root characteristics, yield components, grain yield and nitrogen use efficiency in dryland wheat genotypes and the change will be effective in improving seed quality and quantity characteristics.