90 
WATER REQUIREMENT OF PLANTS. 
Von Seelhorst's experiments on the effect of frequent cutting indi- 
cate that grassland can produce dry matter more efficiently than 
pasture land. In other words, the water requirement of the grasses 
is apparently higher during the earlier stages of growth than at any 
other time. These experiments, however, include the loss due to 
direct evaporation from the soil, which might be greater during the 
earlier stages of the crop. 
A summary of the water-requirement measurements which have been 
made with different crops is given in Table LXXVI. The varia- 
tion in the water requirement of the same crop as determined by 
different investigators is due largely to soil and climatic conditions, 
but probably in part also to the use of different varieties as well as 
to experimental errors. The data given in the same investigation 
are not always strictly comparable, since the crops were not all 
grown during the same period. 
Table LXXVI. — Summary of the water-requirement measurements for various crops, as 
determined by different investigators . 
Crop. 
Lawes, 
1850, 
Rotham- 
sted, 
England. 
Wollny, 
1886, 
Munich, 
Ger- 
many. 
Hellrie- 
gel, 1883, 
Dahme, 
Ger- 
many. 
King, 
1892 
to 1895, 
Madison, 
Wis. 
Von 
Seelhorst , 
1896 to 
1898, Got- 
tingen, 
Ger- 
many. 
Widtsoe, 
1909, 
Logan, 
Utah. 
Leather, 
1910-11, 
Pusa, 
India. 
Briggs 
and 
Shantz, 
1913, 
Akron, 
Colo. 
Wheat 
235 
359 
401 
297 
377 
333 
546 
554 
469 
468 
507 
Oats 
665 
774 
541 
388 
614 
258 
365 
386 
539 
Rye 
724 
233 
350 
386 
337 
437 
369 
306 
Millet 
447 
275 
214 
235 
251 
416 
292 
330 
477 
481 
843 
563 
800 
Clover (sweet) 
709 
Alfalfa 
1,068 
263 
373 
818 
646 
912 
843 
490 
371 
337 
578 
441 
496 
423 
281 
448 
807 
263 
312 
635 
598 
811 
212 
497 
377 
336 
303 
765 
1 
One of the most striking features of water-requirement measure- 
ments is the marked difference in efficiency exhibited by different 
plants in the use of water. The millet, sorghum, and corn groups 
have been found the most efficient, while alfalfa and sweet clover are 
285 
