CEEEAL INVESTIGATIONS AT THE NEPHI SUBSTATION. 



is fairly typical, in its orientation and proportions, of most of the 

 valleys in the intermountain region. It is about 20 miles long from 

 north to south and from 3 to 5 miles wide. South of the city of 

 Nephi a transverse ridge, called the Levan Ridge, crosses the valley 

 from east to west. This ridge, which is rather fan shaped, slopes 

 gradually in three directions from the east, where it abuts upon the 

 base of the mountains. It is from 5 to 6 miles wide, and the crest 

 is about 500 feet above the valley floor, or nearly 6,000 feet above 

 sea level. Dry farming is practiced generally over the ridge. Under 

 the system of alternate fallowing and cropping which is followed, from 

 150,000 to 175,000 bushels of winter wheat are produced annually. 



Fig. 2. — Instruments for recording physical data at the substation, Nephi, Utah. 



The substation is about 6 miles south of the city of Nephi. It com- 

 prises about 100 acres of land, situated near the top of the north 

 slope of the Levan Ridge. Figure 1 shows a view of the Juab Valley 

 in the vicinity of the substation. 



PHYSICAL FACTORS. 



In making a study of crop yields for a series of years it is essential 

 first to have some knowledge of the physical factors which have in- 

 fluenced the growth of the crops. The most important physical 

 factors to be considered are: (1) The soil; (2) rainfall, its distribu- 

 tion and amount during each month and during the year; (3) 

 evaporation, especially that during the crop season; (4) wind, with 

 special reference to that which passes directly over the ground sur- 



