24 CIRCULAR NO. 115, BUREAU OF PLANT INDUSTRY. 



nent sod is established, the banks become covered with Russian 

 thistles, buffalo bur (Solatium rostratinn) , wild oats, sweet clover, 

 and other troublesome weeds. The seeds of these weeds are freely 

 carried by the canal water and are scattered far and wide over the 

 fields. The resulting growth of weeds greatly increases the expense 

 and labor of cultivation. It is practically impossible to produce 

 pure seed crops of grain and alfalfa if weeds are allowed to multiply 

 along the banks of canals and ditches which cut through the fields. 

 The best check to the growth of weeds is a good grass sod. 



Another advantage of the grass covering is to furnish pasturage 

 for live stock. The area occupied by ditch banks can not be util- 

 ized for the production of cultivated crops, but can be made to 

 yield some return when used for grazing. On many of the larger 

 farms the aggregate area that may be made use of in this way is 

 considerable. A half mile of canal bank of medium size has an 

 area of 1 to 2 acres. Moisture is usually abundant on the lower 

 slope of the banks, and a good growth of grass can be secured, which 

 will furnish a fair return for the trouble and expense of seeding. 



NATURE OF THE SOIL. 



The soils of the Bellefourche Project are of two principal types. 

 In the northern part of the area the soils are mostly of the heavy 

 clay loam, known locally as " gumbo." These soils are formed by the 

 weathering of the Pierre shale which underlies the whole area. In 

 the southern part of the project the soils are somewhat lighter on 

 account of the silt and sand which they contain. The unweathered 

 shale which is turned up in many places in building the canal banks 

 is very unfavorable for the growth of grasses, but after a year or 

 two of weathering it is possible to get grass started even in the partly 

 decomposed shale. 



OBSTACLES TO SECURING A STAND. 



Alkali salts are present, although usually in small quantity, in 

 many of the soils of the project. Over the greater part of the area, 

 especially north of the Belle Fourche River, the alkali content ranges 

 from 0.2 to 0.6 of 1 per cent in the first 6 feet of soil. South of 

 the river there is generally less than 0.2 of 1 per cent. The alkali 

 is of a relatively harmless type, consisting mostly of sulphates 

 of calcium, magnesium, and sodium. Fortunately no black alkali 

 (sodium carbonate) is present. Alkali is especially likely to accumu- 

 late along ditch banks because of the high water content of the 

 soil and the high rate of evaporation from the loose surface. This 

 accumulation is especially noticeable in large fills, for in such places 

 some water often seeps through the canal banks. Wherever more 



fCir. 115] 



