Supplemental Irrigation and Water–Yield Relationships for Plasticulture Crops in the Loess Plateau of China

Abstract

Water stress restricts grain yield in the Loess Plateau of China. Two experiments were conducted during three consecutive crop seasons to evaluate benefits of supplemental irrigation from harvested water. Twelve to 48 mm of irrigation was applied at growth stages of corn (Zea mays L.) and winter wheat (Triticum aestivum L.) grown on soil covered with white plastic. Additional 7‐yr wheat and 4‐yr corn experiments focused on the use of plastic for water efficient use. Irrigation increased grain yield, water use efficiency (WUE), and irrigation water use efficiency (IWUE) for all years. The IWUEs from combined use of the plastic and 12 mm of irrigation were 6.36 kg m−3 for wheat at jointing stage and 18.05 kg m−3 for corn at V15 stage in a dry year, with IWUE two to six times greater than WUE. Relative to control conditions, plastic applied at seeding increased WUE from 0.77 to 0.98 kg m−3 for wheat and from 1.52 to 1.94 kg m−3 for corn, but greatest available soil water (ASW) and WUE were achieved when plastic was applied during fallow period before seeding. Grain yield–evapotranspiration relationships were linear with regression coefficients of 1.15 kg m−3 for wheat and 4.56 kg m−3 for corn. Most data points from plastic plots were above the regression line while most from the control plots were below the line, indicating increased WUE by the plastic. The ASW at seeding was more important for wheat than corn because sufficient rainfall normally occurs during corn season while the latter portion of wheat season is usually dry.