Sprinkler irrigation scheme of winter wheat based on water surface evaporation of a 20 cm standard pan

The objective of this paper is to find a simple and easily fulfilling sprinkler irrigation scheduling for winter wheat using the standard 20 cm evaporation pan. An experiment was conducted in 2005-2006 and 2006-2007 winter wheat seasons at Tongzhou Experimental Base for Water-Saving Irrigation Research, Chinese Academy of Sciences. The objective of the experiment was to study the responses of soil water content, winter wheat growth and yield, evapotranspiration and water use efficiency to five sprinkler irrigation amounts, which were 0.25, 0.50, 0.75, 1.00 and 1.25 times of 20 cm pan evaporation (E). Non-irrigation field was arranged as a control. Possibility of making sprinkler irrigation scheduling using 20 cm pan was also discussed. Results showed that soil water content changed greatly within 0-60 cm soil layer under the five sprinkler irrigation conditions. Less sprinkler water amount (<0.25E) limited the leaf area index and dry biomass of winter wheat, and over-amount sprinkler water (>1.00E) also limited winter wheat growth. The seasonal evapotranspiration of winter wheat was between 312 and 508 mm, and generally increased with sprinkler water amount. When sprinkler water amounts were within 0.50 and 0.75 times of pan evaporation, winter wheat yield and water use efficiency were the highest or approaching the highest. While both less sprinkler water (≤0.25E) and over irrigation water (≥1.00E) negatively affected winter wheat yield and water use efficiency. In a conclusion, sprinkler water amount of 0.50-0.75 times of pan evaporation and a sprinkler interval of 5-7 days were recommended for winter wheat cultivation after winter wheat reviving stage in the Beijing area, China.