Water Management in Horticultural Crops

Irrigation water/Cumulative pan evaporation ratio (IW/CPE ratio)

• The use of IW/CPE ratio is suggested as a practical basis of scheduling irrigation. The approach is based on the close and direct relationship of crop evapotranspiration with pan evaporation. When irrigation is applied, water is lost from the soil through evapotranspiration in the same way as the evaporation occurs from an open pan evaporimeter. It is ratio of the amount of irrigation water (IW) applied to cumulative pan evaporation (CPE). The pan evaporation values are added up every day till it is equal to certain ratio of the amount of water applied as irrigation. The ratio for various crops is determined experimentally by estimating the evapotranspiration by lysimeter studies.
  
• The IW/CPE ratios for various crops at different agro climatic conditions in India have been determined under ICAR Coordinated Project for Research on Water Management.