﻿16 BULLETIN 1130, U. S. DEPARTMENT OF AGRICULTURE. 



of rain between harvest and seeding has been large enough to wet 

 thoroughly all the soil on all plats practically every year. This limi- 

 tation of storage capacity has had the effect of eliminating differences 

 between different cultivation methods in the quantity of moisture 

 conserved. Edgeley is the only station included with such a limited 

 water-storage capacity that it has been practically all utilized each 

 year by all methods of cultivation. 



The soil at Belle Fourche is a heavy clay which changes to open 

 partially decomposed shale in the fourth foot. In this soil there is 

 no layer that prohibits moisture penetration, but the soil at the 

 depth of about 2 feet is compact and swells so much when wet that 

 water movement through it is very slow. 6 



Penetration b} r roots is likewise difficult, and even when available 

 moisture has been present in the lower depths the feeding depth of the 

 wheat crop has been limited to a little less than 3 feet. Evidently 

 the roots penetrate into the third foot only as necessity requires, and 

 they have not been able to reach a depth greater than 3 feet before 

 death or the ripening of the crop occurs. For practical purposes there 

 is no need of considering the soil below the third foot. In spite of 

 the limited water-storage capacity of the soil, there have been only 

 two years when plats A and B have been filled to capacity. There 

 has been practically no difference between the two plats in this 

 respect. Plat C or D has been wet to capacity in all but two years. 

 Belle Fourche represents a station where the demands of the crop for 

 water have been so heavy that the soil moisture has been exhausted 

 in all plats each year at harvest. The only exception is plat C or 

 D in 1911. In that year climatic conditions' were so adverse that the 

 crop on the other plats did not germinate and on this plat suffered 

 from drought and heat almost from the time it came up. It made 

 such a limited growth that the roots were not able to extend to a 

 depth of more than 2 feet. 



The soil at Ardmore is a heavy clay that changes into fine sand 

 in the fifth and sixth foot sections. The moisture results show that 

 changes in the water content occur below a depth of 4 feet, but the 

 difficulty in sampling the fifth and sixth foot sections has been so 

 great that sampling has been limited to 4 feet in all but one year. 

 As far as the first 4 feet of soil is concerned, there has been prac- 

 tically no difference in the moisture status of plats A and B. The 

 extent to which plat C or D is superior to plats A and B in moisture 

 stored can not be determined, as changes in moisture content evi- 

 dently have occurred below the fourth foot. The quantity of water 

 used from below the fourth foot, however, can not be large, as plat 

 C or D is little superior to the other plats in point of yield. 



Archer represents a station with a soil depth of approximately 

 4 feet. Below the fourth foot is a bed of gravel that prohibits 

 sampling to a greater depth. It is doubtful whether moisture has 

 penetrated deeper than 4 feet on plats A and B, and in only one year 

 is it probable that water was stored at a depth lower than 4 feet on 

 plat C or D. Plats A and B have approached each other very closely 

 in water stored, utilization of water, and yield. Plat C or D has been 

 little superior to plats A and B in storing moisture. This is re- 



M.-il hews, O. R. Water penetration in the gumbo soils of the Belle Fourche Reclama- 

 tion Project. U. S. Dept. Agr. Bui. 447, 12 pp., 4 fig. 1916. 



