Oct. 15, 1914 



Water Requirement of Plants 



55 



Table XXXII. — Comparison of water-requirement measurements at Akron, Colo., in 



igil and igi2 



Crop. 



Wheat: 



Kubanka 



Bluestem 



Spring Ghirka 



Emmer 



Oats: 



Sixty-Day 



Burt 



Canadian 



Swedish Select 



Barley : 



Hannchen 



Beldi 



White Hull-less 



Beardless 



Rye, spring 



Com: 



Northwestern Dent 



Iowa Silvermine. .. . 



Esperanza 



Sorghum : 



Red Amber 



Milo, Dwarf 



Kafir, Blackhull . .. 



Durra, White 



Kaoliang, Brown . .. 



Millet, German 



Legumes: 



Alfalfa 



Clover, sweet 



Beet, sugar 



Mean water-requirement ratio for 1912 to 

 191 1 



Mean evaporation ratio for June, July, and 

 August, igi2 to 1911 



Water requirement. 



468 ±8 

 S3i±5 

 506 ±3 

 534±i4 



60s ±5 



639 ±7 



598±i4 



6i5±7 



527±8 

 543 ±2 

 S42±3 

 544±9 

 724±7 



368±io 



420±3 



3i9±S 



298±4 



333 ±3 

 278±5 



32I±2 



301 ±3 

 263±i5 



i,o6S±i6 

 709 ±9 

 377±8 



394±7 

 45i±4 

 4S7±3 

 428±3 



491 ±13 

 449 ±3 

 399 ±6 

 423 ±5 



443 ±3 

 4i6±4 



439 ± I 

 403 ±8 

 496 ±9 



28o±io 



3°2±7 



239±3 



237±4 

 273±4 

 259±S 

 255±3 



223±I 



248 ±7 



659±6 

 638±4 

 32i±8 



Ratio. 191J 

 to igii. 



O. 84 ±0. 02 

 .85± .01 

 . 9oi: . 01 

 . 8o± . 02 



.8i± .02 

 • 7o± . 01 

 . 67± .02 

 . 69± . 01 



. 84± . 01 

 . 76± . 01 

 .8i± .01 

 . 74± • 02 

 . 69± . 01 



■75± -03 

 . 72± .02 

 . 79± .01 



. 8oi: . 02 

 . 82 ± .02 



■ 93± -02 

 . 79± . 01 

 . 74± -oi 

 .94± -05 



. 62 ± .03 

 . 90± . 02 

 .85± .03 



79± .02 



■75± -03 



Evaporation measurements from a free-water surface at Akron are 

 also available for igii and 1912 (Briggs and Belz, 1910, p. 17). The 

 ratio of the evaporation in 1912 to that in 191 1 by months is as follows: 

 June, 0.69; July, 0.78; August, 0.79. The average ratio during these 

 three months is 0.75 ±0.03. This corresponds to a reduction of 25 ±3 

 per cent in evaporation as compared with a reduction of 21 ±2 per cent 

 in the water requirement. The change in the water requirement of 

 these 25 varieties taken together is seen to be in approximate agreement 

 with the change in evaporation from a free-water surface. A consid- 

 eration of the individual ratios indicates, however, that different varie- 

 ties may respond quite differently to the same change in climatic con- 

 ditions. 



To investigate further the variation in water requirement due to 

 differences in climatic conditions, a number of varieties were also 



