Managing Global Resources for a Secure Future

Improving resource-use efficiency is vital for sustainable agricultural production in water-scarce regions such as North China Plain. Data from a two-factorial field experiment carried out during 2015-16 at Luancheng Agro-Ecosystem Research Station (China) were used to assess the effects of irrigation and straw-mulch on radiation interception (IPAR), radiation-use efficiency (RUE) and water-use efficiency (WUE) of winter wheat (Triticum aestivum). The factors included two irrigation levels viz. full (FI) and deficit (DI) (200 and 100mm + rainfall, respectively), and two mulching strategies viz. mulch and no-mulch (~8 and 0 Mg ha^-1, respectively). Light interception was estimated from weekly measurements of spectral reflectance after the start of regrowth in spring. Total evapotranspiration from sowing to harvesting was estimated with water-balance equation, validated with soil water measurements during the season, and used to calculate WUE. Mulching significantly reduced IPAR (12-15%), increased RUE (12-14%) and WUE (7% only for DI), but had no sizeable effect on grain yield and final biomass. IPAR was mainly affected between tillering and anthesis stages through effects on tiller number, spike differentiation and leaf area index. DI significantly increased WUE (8-20%), reduced IPAR (4-8%) but had no effect on RUE. DI also reduced grain yield and final biomass by 4-5% and 2-7%, respectively. Maximum estimated WUE under DI with mulch was 24 kg grain ha^-1 mm^-1, which is slightly higher than reported by FAO (22 kg grain ha^-1 mm^-1). Results imply that light interception is important but it has to be coupled with early vigor. Light intercepted by weak seedlings/tillers before anthesis may not contribute to final yield and biomass because severe competition during later stages kills all the weak tillers. Deficit irrigation in combination with straw mulch is a viable option to improve RUE and WUE of wheat with a small yield penalty; however, applying mulch with full irrigation is not an effective strategy.