Evapotranspiration efficiency of pea in south and central Alberta

Evapotranspiration (ET) efficiency regulates suitability and management of crops on the Canadian prairies. To evaluate the ET efficiency of pea (Pisum sativum L.), soil water depletion and yields as a function of precipitation were determined for Carneval pea at 28 sites in south and central Alberta from 1995 to 1998. Soil water depletion between seeding and harvest was as high as 112 mm at sites with high levels of available soil water at seeding and low to moderate levels of precipitation. Pea was capable of extracting soil water to a depth of about 0.6 in at most sites, but extraction of soil water below this depth was much more variable. At sites where soil water did not limit the depth of soil water extraction, a negative correlation was observed between the maximum depth of effective soil water extraction and the sum of maximum temperature degree-days above 25.6degreesC. The ET efficiency of pea seed yield ranged from 7.5 to 19.1 kg ha(-1) min(-1), with an average value of 13.0 kg ha(-1) mm(-1). No correlation was observed between ET efficiency and weather variables, such as average temperature, vapor pressure deficit or length of the growing season.