Nitrogen Recovery Efficiency and Grain Yield Response Index of Some Wheat Varieties as Affected by Nitrogen Fertilizer Rates

Considering the importance of nitrogen as a critical factor in agriculture and the high costs of nitrogen fertilizers, its benefit must be maximized.So, studies evaluating nitrogen use efficiency (NUE), nitrogen agronomic efficiency (NAE) and Grain yield response index (GYRI) are becoming increasingly necessary in crop production.Therefore, two field experiments were conducted in splitplot design during the 2018/2019 and 2019/2020 seasons to evaluate the productivity of four wheat varieties (Gemmiza-11, Giza-168, Misr-1 and Sids-12) under five nitrogen (N) fertilizer rates (0, 30, 60, 90 and 120 kg N fed -1 ).The results showed significant differences among wheat varieties in both seasons for yield and its components as well as NUE and its attributes.Misr-1 gave the highest values of number of spikes m -2 , number of grains spike -1 , grains yield fed -1 , total N uptake and NUE.However, Sid-12 recorded the highest straw yield and the heaviest 1000 grain weight obtained by Gemmiza-11.Giza-168 recorded the highest N uptake and N content in grains and straw.Increasing N fertilizer rates from 0 to 90 kg N fed -1 increased yield and its components, as well as grains N%, straw N%, grains N uptake and straw N uptake but decreased NUE.Yield, its components, NUE, and its attributes were affected significantly by the interaction among wheat varieties and N fertilizer rates in both seasons.The maximum NAE was recorded with Misr-1 and with 90 kg N fed -1 .GYRI values showed that Misr-1 and Gemmiza-11 belonged to the efficient-responsive group in both growing seasons.