CEEEAL EXPERIMENTS AT THE WILLISTON SUBSTATION. 3 



PHYSICAL FACTORS. 



A summary of crop yields for a series of years should be accom- 

 panied by a statement of the physical factors that influence crop 

 production. The most important physical factors are (1) the soil; 

 (2) the seasonal and annual rainfall; (3) the seasonal evaporation; 

 (4) the wind, with special reference to that which passes directly over 

 the ground surface during the growth of the crop; and (5) the tem- 

 perature, especially the killing frosts of spring and autumn that limit 

 the growing season. The data on these factors, which follow, have 

 been recorded at the Williston substation and at the station of the 

 United States Weather Bureau in Williston. 



The soil of the Williston substation is of an alluvial character, but 

 it is variable in type. It is not typical of most of the best farming 

 land outside of the valley. The creek-bottom flat consists of a heavy 

 clay of the type described by the Bureau of Soils as Laurel clay. 

 The larger portion of the substation consists of level or rolling land 

 somewhat higher than the creek bottom. The somewhat variable 

 soil on this portion is of the type known as Williston sandy loam. 

 Water for irrigation is available on this part of the station farm. 



That portion of the substation where the cereal experiments are 

 conducted consists of a fairly level upland area, on which irrigation 

 water is not available. The soil, which is fairly uniform in type, is 

 classed as Laurel fine sandy loam. 



NATIVE VEGETATION. 



A biological survey was made of the Williston area in 1906. 2 The 

 most important native vegetation found prevailing on the prairie 

 included grama grass (Bouteloua oligostachya) , buffalo grass (Bul- 

 bulis dactyloides) , western wheat-grass (Agropyron occidentale) , slender 

 wheat-grass {Agropyron tenerum), and needle grass (Stipa comata 

 and Stipa viridula). The grama grass grows abundantly over the 

 prairie and makes a very nutritious pasture and excellent hay. The 

 buffalo grass is just as nutritious, but is found more in spots and is 

 never tall enough for hay. The western and slender wheat-grasses 

 are found in the wild state and will replace the other native grasses 

 when the sod is broken. They are grown extensively for the produc- 

 tion of hay. 



RAINFALL. 



Table 1 shows the precipitation record for the Williston locality 

 for a period of 36 years, from is?'.) to 1914, inclusive. Previous to 

 1893 the weather records were kept at Fort Buford, N. Dak., 20 



i I or a full report on the soils of fbe WflUstoii local Ity, see Rice, T. D.,WUlard,R. B.,and Weaver,!. T;, 

 of the Williston arm, North Dakota. In U.S. Dept. A^r. itur. Soils Field Oper, 1906,8th Rpt., 

 1022, flg, 34, 1908, 

 >BeU,W. B. Report of the biological survej of North Dakota. In 4th Bleu. Rpt. Agr. Col. Sur- 

 rey N. L>ak , p, 28-61, 1910. 



