6 BULLETIN 39, U. S. DEPARTMENT OF AGRICULTURE. 
clay containing rounded granitic stones commonly known as " hard- 
heads.'' These glacial soils are well suited to cereal production. The 
soils west of the Missouri River are alluvial or residual in their 
origin, that is, they are either the result of deposits of sediment or 
were formed in place by the disintegration of the underlying rocks. 
For this reason these soils are extremely variable. Several types 
of soil may be found on the same farm. The general soil types 
include a sandy loam in the southern, a sticky clay in the central, 
and a silt loam in the northern part of this section. 
The soil of the Brookings field is a medium sand} 7 loam, that of 
the Highmore field a medium clay loam, that of the Eureka field a 
sandy loam, and that of the Cottonwood field a sticky clay, known 
locally as gumbo. 
Thus, the four fields represent, in a general way. the common soil 
types of the State. However, there are many local variations in the 
character of the soil which may influence the results when the crops 
here discussed are grown on other farms. 
HISTORY OF THE COOPERATIVE EXPERIMENTS. 
The cooperative study of the grain crops in South Dakota was 
begun in 1903 by the South Dakota Agricultural Experiment Station 
and the Office of Cereal Investigations of the United States Depart- 
ment of Agriculture. The first purpose of the work was to determine 
what varieties were best adapted to South "Dakota conditions. Sev- 
eral hundred introductions were made from various parts of the 
world and were placed on trial. Many were found to be entirely 
unfit the first season, while others were grown for several years before 
it could be definitely determined whether they were suitable. The 
varieties discussed in this bulletin are the best of the many which 
were tested. After having learned something of the relative value 
of the different varieties, work was begun in 1910 toward the improve- 
ment of the best ones. 
Portions of the work have been reported from time to time in 
various bulletins of the South Dakota Agricultural Experiment 
Station x and of the United States Department of Agriculture. 2 The 
1 Shepard, J. H. Macaroni wheat : its milling and chemical characteristics. South 
Dakota Agricultural Experiment Station, Bulletin S2, 45 p.. 6 pi., 1903. 
Chilcott, E. C. and Cole, J. S. Cooperative cereal investigations at Highmore. Sum- 
mary of results for 1903. South Dakota Agricultural Experiment Station. Bulletin S4. 
p. 9-14, 1904. 
Shepard, J. H. Macaroni wheat ; its milling and chemical characteristics and its 
adaptation for making bread and macaroni. South Dakota Agricultural Experiment 
Station, Bulletin 92, 39 p., 4 pi., 1905. 
Cole, J. S., and Balz. Sylvester. Cereal investigations at Highmore. South Dakota 
Agricultural Experiment Station, Bulletin 96, p. 45-60, fig. 4, 1906. 
Shepard, J. H. Macaroni or durum wheats. (A continuation of Bulletin 92.) South 
Dakota Agricultural Experiment Station, Bulletin 99, p. 105-115, 1906. 
