52 BULLETIN 142, U. S. DEPARTMENT OF AGRICULTURE. 



The length of the growing season, or the normal interval between 

 killing frosts in spring and fall, varies widely in the different sec- 

 tions of this territory. Thus in the southern areas, in southern and 

 central Ohio and Indiana, the length of the growing season is ap- 

 proximately 175 days. The season becomes gradually shorter toward 

 the north, comprising only about 150 days in central Michigan and 

 Wisconsin. Only the most northern developments of the soils of 

 this series have a growing season as short as 125 days under normal 

 onditions. 



Since the differences in altitude within this section are in general 

 slight, there are no marked departures from the normal changes 

 in climatic condition caused by differences in elevation. The pro- 

 tective influence of large bodies of water is felt in the case of those 

 areas of the series which lie along the eastern shore of Lake Mich- 

 igan to a distance of 30 miles or more inland, and, to a less extent, in 

 areas along the western shore of the lake and around Green Bay. 



These climatic conditions render possible the production of prac- 

 tically all of the staple crops suited to a temperate climate. 



In considering the crop uses and adaptations of the different soils 

 of the Miami series it must be held in mind that the different types 

 are very unequally distributed through the region in which the series 

 is developed. Fully 80 per cent of the total area of the Miami clay 

 loam thus far encountered in the soil surveys lies in Ohio and Indi- 

 ana. Approximately 50 per cent of the Miami silt loam has been 

 encountered in these two States, while additional large areas occur 

 in the southeastern part of Wisconsin where the climatic conditions 

 are not materially different. All of the Miami fine sandy loam thus 

 far mapped occurs in Michigan and Wisconsin, while the other more 

 sandy and gravelly types, which are subordinate in total area, are 

 chiefly confined to Wisconsin. 



This uneven distribution of the types of the series will probably 

 be accentuated as the soil survey work progresses, since it is known 

 that large additional areas of the Miami clay loam and silt loam 

 exist in western Ohio and central Indiana. There is thus a prepon- 

 derance of the heavier soil types in the more southern latitudes and 

 of the more sandy or loamy types farther north. 



Moreover, the gravelly soils of the series and large areas of the 

 more sandy soils are marked by a rather rough topography, and are 

 less well suited to agriculture than the smoother, heavier members 

 of the series. 



All of these circumstances tend toward the partial development 

 only of the sandy and gravelly soils and toward a restricted crop 

 use, while the fine sandy loam and heavier members of the series are 

 extensively occupied for the production of a wide range of staple 

 crops. 



