Nitrogen Use Efficiency of Wheat Lines Evaluated for Forage.

Wheat is the most common winter pasture in the Southern Great Plains. When wheat is utilized in a grazing system or dual-purpose more nitrogen is required compared to grain-only production. Our objective is to evaluate the Nitrogen Use Efficiency (NUE) of dual-purpose wheat lines based on forage production. Twenty lines of winter wheat were evaluated in greenhouse for NUE in four N rates: 0, 75, 150 and 300 mg of N.Kg^-1 of soil. Four seedlings of each line were planted in gallon pots containing a mixture of Metromix (580) and pasteurized soil of low N content. The experiment was laid out in a randomized complete block design with a two-level factorial arrangement of three replicates. The wheat plants were harvested 4 times (every 3-4 weeks) to estimate dry matter (DM) production. The N content of the samples was estimated through NIRS. The DM and N content were utilized to calculate Nitrogen uptake efficiency (NUpE), Nitrogen utilization efficiency and NUE. The statistical analysis indicated differences among lines and the N rates for DM, NUtE, and NUE (P>0.0005). Significant variations for NUpE was found only among the N rates (P >0.0001). Line x N rate interaction was not significant for any variable evaluated. The average NUE at 75 mg of N.Kg^-1 was 29.7 g.g^-1 reducing to 26 g.g^-1 and 21.5 g.g^-1 as more N was applied, 150 and 300 mg of N.Kg^-1 respectively. The top ranked lines for the rates 75 and 150 mg of N.Kg^-1 (BigSky) and 300 mg of N.Kg^-1 (NF97117) were 16%, 15% and 8% more N use efficient than average, respectively. The same lines were also evaluated in hoop-house to better reproduce field conditions following similar design and protocol described above. Based on the results high and low NUE wheat lines will be selected to be evaluated in real field conditions.