10 



BULLETIN 1004, U. S. DEPARTMENT OF AGRICULTURE. 



average rate of use at Archer agrees with the rate in North Dakota 

 and South Dakota. This station is located at an altitude of more 

 than 6,000 feet and has a summer temperature, evaporation, and other 

 climatic factors more nearly like the Northern States than stations 

 in the same latitude. 



Table 2. — Rate of the use of icater per day during a period of rapid growth on 

 both plats A and C or D averaged for each station. 



Station. 



Huntley 



Williston 



Dickinson 



Mandan 



Edgeley 



Hettinger 



Belle Fourche 



Use of water. 



Plat 

 A. 



Inch. 

 0.14 

 .15 

 15 

 15 

 17 

 15 

 15 



Plat 

 CorD. 



Inch. 

 0.20 

 .21 

 .20 

 .15 

 .16 

 .19 

 .18 



Station. 



Ardmore 



ScottsblufL. 

 North Platte 



Archer 



Akron 



Garden City. 

 Amarillo 



Use of water. 



Plat 

 A. 



Plat 

 CorD. 



Inch. 



Inch. 



0.21 



0.20 



.18 



.21 



.20 



.23 



.15 



.15 



.20 



.20 



.17 



.22 



.24 



.30 



With plat C or D the regional effect is more obscured by the in- 

 fluence of the size of the crop on the rate of use. It is most fully 

 exemplified in the high rate at Amarillo, which averages 0.3 inch 

 per day. This is the average of the rates of 0.33 inch and 0.26 inch, 

 respectively. One of these is the highest yet determined and the 

 other has been equaled only once, which was at North Platte in 

 1909. The rates of use at North Platte and at Garden City also 

 average high in comparison with those at more northern stations. 

 Archer has a comparatively low rate on this plat, the same as on 

 plat A. 



In general terms, the average rate of use on plat A ranges from 

 an average of 0.15 inch per day at the northern stations to 0.24 inch 

 at the most southern station and on plat C or D from nearly 0.2 

 inch per day at the northern stations to 0.3 inch at the station farthest 

 south. The most southern station therefore shows a daily rate of 

 use from 50 to 60 per cent greater than the northern stations. 



The averages of plats A and C or D show a relation between the 

 rate of use and yield. A close correlation between the two should 

 not be expected, because the rate of use of water was determined 

 for a period that covered only part of the life of the crop. 



In many cases the crop suffered severely from drought at some 

 time after this rate was determined. Other factors, such as ex- 

 tremely hot weather, may have influenced it after the rate had been 

 determined. It was thought, however, that if any relation between 

 the rate of use of water and yield existed, it would be shown through 

 a positive correlation, even though the correlation might not be 

 strong. 



The first correlation was made by using the average yield and the 

 average rate of all stations as bases from which to compute de- 

 partures. The resulting correlation for plat A was 0.24, with a 

 probable error of ±0.09. This is a very weak correlation and onlj- 

 indicates that a relation may exist. It was not thought possible 

 that a close correlation can be arrived at in this way. The facts 

 that the northern stations yield heavier than the southern ones and 



