Drought stress is one of the main limitations to crop growth and yield. Efficient nitrogen (N) nutrition may moderate the negative effects of drought stress on plants through retention of metabolic activities. The present study was conducted to investigate the biochemical responses of two millet species, foxtail millet (Setaria italica (L.) P.Beauv.) and proso millet (Panicum miliaceum L.), under two irrigation regimes (based on 55% and 85% soil-water depletion) and two N fertiliser levels (0 and 112.5 kg N ha–1) at four sowing dates (22 June and 6 July 2015, 14 and 30 June 2016). Drought stress increased hydrogen peroxide (H2O2), malondialdehyde (MDA) and other aldehyde contents of the plants, ultimately leading to 52% and 55% reductions in grain yield in foxtail millet and proso millet, respectively. Antioxidant activities showed significant increases under drought stress. Nitrogen application decreased H2O2, MDA and other aldehyde contents and activities of antioxidant enzymes, whereas it increased chlorophyll, carotenoid, phenolic compound and proline contents as well as grain yield. Higher grain yields were obtained with early planting dates under sufficient water supply, whereas superior yields were obtained with delayed planting dates under water stress owing to lower temperatures and evaporation rates. The results suggest that N application could mitigate the adverse effects of drought stress on millet plants by promoting osmoregulation, alleviating lipid peroxidation, and improving plant physiological traits. Foxtail millet had higher antioxidant potential than proso millet, resulting in greater capacity to inhibit production of free oxygen radicals and making it the more drought-tolerant species.

This study was conducted to investigate the effects of two irrigation regimes (55 and 85% of soil available water depletion) and two nitrogen levels (0 and 112.5 kg ha⁻¹) on yield as well as water and nitrogen use efficiencies of two millet cultivars (namely, Bastan and Pishahang) planted at two sowing dates during 2015 and 2016. Growth parameters and nitrogen use of the millet cultivars were found affected by drought, nitrogen level, and sowing date as well as their interactions. Nitrogen application was found to improve not only nitrogen uptake, chlorophyll content, and irrigation water use efficiency (IWUE) but also grain and biological yields; more positive effects were, however, observed under the control irrigation regime. Nevertheless, nitrogen uptake (NUpE), utilization (NUtE), and use (NUE) efficiencies decreased as a result of nitrogen application. The increases in grain yield (16 versus 7%) and IWUEg (17 versus 6%) due to nitrogen application were more pronounced in the drought-tolerant Bastan cultivar than in the drought-sensitive Pishahang. However, nitrogen application decreased NUpE in both cultivars. Although water stress increased soil N residual with all the sowing dates, the increase was greater with the early ones. The results of the experiment suggest that the application of higher nitrogen levels is not the proper strategy for compensating for the reduced yield under drought conditions. Rather, late sowing dates, due to the lower drought effects associated, might be the proper alternative for achieving higher yields as well as improved IWUE and NUE in areas plagued with water shortage.