<P> Recognizing the challenge of cultivating marginal arid land, the United States government expanded on the 160 acres (65 ha) offered under the Homestead Act--granting 640 acres (260 ha) to homesteaders in western Nebraska under the Kinkaid Act (1904) and 320 acres (130 ha) elsewhere in the Great Plains under the Enlarged Homestead Act (1909). Waves of European settlers arrived in the plains at the beginning of the 20th century . A return of unusually wet weather seemingly confirmed a previously held opinion that the "formerly" semiarid area could support large - scale agriculture . At the same time, technological improvements such as mechanized plowing and mechanized harvesting made it possible to operate larger properties without increasing labor costs . </P> <P> The combined effects of the disruption of the Russian Revolution, which decreased the supply of wheat and other commodity crops, and World War I increased agricultural prices; this demand encouraged farmers to dramatically increase cultivation . For example, in the Llano Estacado of eastern New Mexico and northwestern Texas, the area of farmland was doubled between 1900 and 1920, then tripled again between 1925 and 1930 . The agricultural methods favored by farmers during this period created the conditions for large - scale erosion under certain environmental conditions . The widespread conversion of the land by deep plowing and other soil preparation methods to enable agriculture eliminated the native grasses which held the soil in place and helped retain moisture during dry periods . Furthermore, cotton farmers left fields bare during winter months, when winds in the High Plains are highest, and burned the stubble as a means to control weeds prior to planting, thereby depriving the soil of organic nutrients and surface vegetation . </P> <P> After fairly favourable climatic conditions in the 1920s with good rainfall and relatively moderate winters, which permitted increased settlement and cultivation in the Great Plains, the region entered an unusually dry era in the summer of 1930 . During the next decade, the northern plains suffered four of their seven driest calendar years since 1895, Kansas four of its twelve driest, and the entire region south to West Texas lacked any period of above - normal rainfall until record rains hit in 1941 . When severe drought struck the Great Plains region in the 1930s, it resulted in erosion and loss of topsoil because of farming practices at the time . The drought dried the topsoil and over time it became friable, reduced to a powdery consistency in some places . Without the indigenous grasses in place, the high winds that occur on the plains picked up the topsoil and created the massive dust storms that marked the Dust Bowl period . The persistent dry weather caused crops to fail, leaving the plowed fields exposed to wind erosion . The fine soil of the Great Plains was easily eroded and carried east by strong continental winds . </P> <P> On November 11, 1933, a very strong dust storm stripped topsoil from desiccated South Dakota farmlands in just one of a series of severe dust storms that year . Beginning on May 9, 1934, a strong, two - day dust storm removed massive amounts of Great Plains topsoil in one of the worst such storms of the Dust Bowl . The dust clouds blew all the way to Chicago, where they deposited 12 million pounds of dust . Two days later, the same storm reached cities to the east, such as Cleveland, Buffalo, Boston, New York City, and Washington, D.C. That winter (1934--1935), red snow fell on New England . </P>

Which of the following did not contribute to the dust bowl in the 1930’s