Productivity and Radiation Use Efficiency of Four Dryland Wheat Cultivars under Different Levels of Nitrogen and Chlormequat Chloride

The impact of climate change in the next few decades will increase risks of wheat
production under dryland conditions. Therefore, it is important to find cultivars that are
tolerant to these conditions and can provide reasonable yield under future climates.
Radiation use efficiency (RUE) is the key factor determining the crop yield and is related
to crop biomass and leaf area index (LAI). To obtain a high yield from a given cultivar
under dryland conditions, it is necessary to achieve optimum RUE. In this study, the
effects of different levels of nitrogen fertilizer (N) and plant growth retardant
(chlormequat chloride= CCC) on LAI, dry matter accumulation, biomass yield, and RUE
of four dryland wheat cultivars were examined. The field experiment was carried out
during 2006-07 and 2007-08 growing seasons at the experimental agriculture research
station of Shiraz University, Iran. The results suggested that different cultivars varied
significantly in LAI, biomass and RUE under similar conditions and demonstrated the
dependency of RUE on LAI and biomass yield. During 2006-07, the highest biomass
production (431.2 g m-2) and RUE (0.99 g MJ-1 m-2) were obtained from Nicknejad
cultivar, CCC application, and using 80kgN.ha-1. During 2007-08, the highest biomass
production (333.5 g m-2) and RUE (0.76 g MJ-1 m-2) were obtained from Azar-2 cultivar,
CCC application, and 80 kg N ha-1. Based on the results of this study, application of N and
selecting cultivars resistant to late season drought stress could be considered for
improving RUE in dryland farming.