6 CIRCULAR 5 6 3, IT. S. DEPARTMENT OE AGRICULTURE 



was wet 3 and 2 feet, respectively. The yields were higher than on 

 the continuously cropped plots but were of low order. In the other 

 5 years the fallowed plot had 3 feet or more of wet soil, and the yields 

 were somewhat higher than those on the continuously cropped plots. 



Huntley 



Data from the Huntley station are available for all but 1 of the 

 27 years 1912-38. There were no soil-moisture determinations in 

 the spring of 1917. On land continuously cropped to wheat water 

 seldom penetrates to a depth of more than 2 feet. In about half 

 the years the depth of wet soil did not exceed 1 foot, and in only one 

 of these was a good yield obtained. In one other year when this 

 condition obtained the spring-plowed plot produced 11.0 bushels and 

 the fall-plowed plot 7.8 bushels. When the soil was wet 2 feet deep 

 there was something less than an even chance of getting a good yield. 



On fallowed land there were about the same number of years with 

 2 feet of wet soil as on continuously cropped ground, but there was 

 a sharp decrease in the number of years with 1 foot of wet soil and 

 an increase in the number having 3 feet or more of wet soil. 



During the 8 years 1930-37 the third foot was not wet even on 

 fallowed land, and the crop failed or yields were very low. 



Dickinson 



During the period 1907-38 in which crops have been grown on the 

 Dickinson station there are 21 years in which data are available for 

 the present study. In 1912 and 1914 the crops were destroyed or 

 severely damaged by hail. In 1931 cutworms destroyed the normal 

 crop and necessitated a late reseeding. Other years from 1918 to 1938 

 are omitted because soil-moisture determinations at an appropriate 

 time in the spring are lacking. 



There was a proportionate increase in average yields with successive 

 increases in the depth of wet soil in the spring. At this station 3 feet 

 or more of wet soil provides as high a degree of assurance of a satis- 

 factory yield as can be expected, and 2 feet of moist soil offers better 

 than an even chance of such a return. 



Mandan 



Data are available from two fields at Mandan. The soil of the main 

 field is light, and that of the south field is heavy. A 24-year record is 

 available from the main field and a 20-year record from the south field. 

 The average penetration of water is greater in the main than in the 

 south field and yields are higher (2, 9). On land continuously cropped 

 to wheat the soil is wet to a depth of 2 feet much more frequently on 

 spring-plowed than on fall-plowed land in the main field. The record 

 on fall-plowed land in the south field is too short for adequate compar- 

 ison. In both fields 3 feet or more of wet soil provides a high degree 

 of assurance of a crop. With less than 3 feet of moist soil in the spring, 

 the average yields are materially lower and the chances of failure or a 

 low yield are greatly increased. 



