Abstract:
An experiment was conducted to investigate the relationship between reference crop evapotranspiration(
ET0) and actual crop evapotanspiration
(ET), and relationship among crop coefficient
(Kc), leaf area index
(LAI) and plant height
(H) at winter wheat elongation-heading stages during 2000~2002 winter wheat season at Yucheng Comprehensive Experimental Station and 2002~2004 season at Tongzhou Experimental Base. Results show that
ET measured using lysimeters was lower than or near to
ET0 computed using FAO 56PM method at the beginning of wheat elongation-heading stages and then increased higher than
ET0 at the end of the stage. Crop coefficient, the ratio of
ET to
ET0, increased with
LAI and
H. The mathematical relationships between
Kc and
LAI and
H were developed using datasets in2003 and 2004.
ET values in 2001 and 2002 were estimated using above relationship incorporated with
ET0. The estimated
ET values computed using both
LAI and
H methods agreed well with the measured except when
ET was less than 3 mm/d, which might be because of higher soil evaporation at the beginning of the stageunder small
LAI level. The estimated
ET computed using both methods showed that there was no significant difference between
LAI method and
H method, andtherefore
H method could be used to estimate crop evapotranspiration at wheat elongation-heading stages in the North China Plain.