12 LAND DRAINAGE 



ing of the next is no doubt often thought of as one of rest 

 as synonymous with idleness. It is not often considered 

 as a period of rest in the sense of recuperation, as it should 

 be. After producing certain crops, and especially under 

 abnormal weather conditions, the soil is found to be in a 

 very unsatisfactory physical condition, and one in which 

 the evils are cumulative, or may easily become so if proper 

 precautions are not taken. Who has not seen the wheat 

 field, the oat field, and even the bean field, so baked and 

 scorched as to make it seemingly impossible of prepara- 

 tion for an immediate crop ? In this condition of intensely 

 high temperature and dryness, not only are certain im- 

 portant processes suspended, but undoubtedly much of 

 the desirable microscopic flora is destroyed. 



19. Actual temperatures. In the humid part of the 

 United States, soils under normal weather conditions are 

 seldom, if ever, too warm for the ordinary crops. The 

 opposite is more likely to be true, so that when the tiller 

 has exercised his highest art in soil management, the 

 temperature still ranges too low for the best results in 

 cropping. In Table IV data have been assembled to show 

 average soil temperatures for the growing months as 

 gathered at rather widely distributed points and under 

 different conditions. Note the average soil temperature 

 for 6 inches deep in parts 1, 2, 3, and 6 of the table. 

 Observe that in no case does the average reach the opti- 

 mum for seed germination. This <Ioes not occur even at 

 1 inch deep in Nebraska, nor at 3 inches deep in Geneva. 



It should be borne in mind, however, that these tem- 

 peratures are expressed as monthly averages. On some 

 days the maximum temperature would much exceed the 

 average of the month, and even at 6 inches deep might 

 approach optimum. 



