Improved Water Use Efficiency Associated with Cultivars and Agronomic Management in the North China Plain

Abstract

Both winter wheat (Triticum aestivum L.) and maize (Zea mays L.) are the two staple crops of the North China Plain (NCP) that are combined in a single‐year rotation. While annual evapotranspiration increased slightly, field studies conducted at Luancheng Station indicated that crop yield improved by 50% and resulted in significant water use efficiency (WUE) increases from 1982 to 2002. Water use efficiency has improved from 10 to 15 kg mm−1 ha−1 for winter wheat and from 14 to 20 kg mm−1 ha−1 for maize in the Piedmont of Mt. Taihang in the NCP. Yield increase was associated with the increase in kernel numbers per unit area without alteration of the weight of the kernels for both winter wheat and maize. Number of kernels per spike of winter wheat was increased from about 22 for cultivars used in 1980s to about 28 for cultivars used presently. Number of kernels per ear of maize was increased from about 300 for cultivars used in 1980s to about 450 presently. From the early 1990s, combine had been used to harvest winter wheat, allowing straw mulch to be applied to maize. Measurements of WUE from 1987 to 1992 and again from 1997 to 2002 showed that WUE of maize under mulch was significantly higher than that without mulch. Mulching reduced soil evaporation loss by 40 to 50 mm per annum measured by microlysimeters, and WUE was averagely improved 8 to 10% for the 12 seasons. An improvement in irrigation scheduling had also improved WUE. Irrigation applications to winter wheat were reduced from about eight times in 1980s to about four times presently. Field tests from 1999 to 2004 still showed that reducing the present number of seasonal wheat irrigations to either three, two, or one depending on seasonal rainfall would benefit both grain production and WUE of winter wheat.