paragraphs, a definite relationship exists between evapotranspi- 

 ration and rates of evaporation from pans or atmometers . This 

 relationship is considered fundamental to estimating evapotranspi- 

 ratlon for other crops and in other agricultural areas throughout 

 the State. 



The ratio of evapotranspiration (ET) to evaporation from 

 an evaporation pan (Ep) is referred to as a "pan coefficient" 

 (ET/Ep) ; in like m.anner, the ratio of evapoti-anspiration to net 

 atmometer evaporation^ or the difference of evaporation from a 

 black and white Livingston Spherical Atmometer (Eb-w), is referred 

 to as the "atmometer coefficient" (ET/eb-w) . 



Pan and/or atmometer coefficients for individual evapo- 

 transpiration measurement periods for the various plots sampled 

 are shown in Appendix A in Tables A-6 and A-7. A casual examina- 

 tion of these individual periods reveals v;ide variations which 

 v/ould appear to discount the validity of such comparisons. How- 

 ever, a more detailed analysis of the data indicates that ce^-tain 

 relationships do exist, and upon such relationships tentative 

 values can be established. Certain variations of the pan and at- 

 mometer coefficients from time to time are caused by plants re- 

 sponding differently to evaporation influences than do pans and 

 atmometers. Likewise, variations in the coefficients were due 

 also to individual differences in the response of atmometers or 

 pans to these climatic influences. 



Analysis of data for each individual crop and the con- 

 clusions drawn therefrom are discussed in the follo\\fing paragraphs 



56- 



