The effect of nitrogen splitting on some agronomic and physiological traits of two corn cultivars under normal irrigation and drought stress

To examine the effect of nitrogen splitting on some agronomic and physiological traits of two corn cultivars under normal irrigation and drought stress, a factorial split plot experiment was implemented in Tehran (Iran) in 2017-2019. Main factors included irrigation at two levels of normal irrigation (I1: irrigation after 60-mm evaporation from Class A pan) and stress (I2: irrigation after 120-mm evaporation) and nitrogen splitting at four levels (N1: 1/2 after emergence + 1/2 after 8-leaves stage, N2: 1/3 after emergence + 1/3 after 8-leaves stage + 1/3 after emergence of male inflorescence, N3: 1/4 after emergence + 1/2 after 8-leaves stage + 1/4 after emergence of male inflorescence, and N4: 1/4 after emergence + 1/4 after 8-leaves stage + 1/2 after emergence of male inflorescence) and sub-factor of cultivar was considered at two levels (C1: Single cross 704 cultivar and C2: Maxima cultivar). Drought stress significantly declined the number of seed rows per cob, 100-seed weight, and relative humidity, and significantly increased proline and abscisic acid contents. Maxima cultivar had the highest proline content and abscisic acid activity in N1 fertilizer treatment and under stress conditions. With an average of 9541 kg ha-1, N3 treatment had the highest seed yield. Single cross 704 cultivar exhibited more resistance to drought stress and nitrogen deficiency. Consequently, it may be used in arid climates. Proper nitrogen splitting could enhance yield in both corn cultivars even under stress conditions. Thus, the effect of this key factor on improving corn yield should be considered.