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AGRICULTURE IN THE SEMIARID GREAT PLAINS. 



Conservation of moisture is not the only benefit derived from sum- 

 mer tillage, although it is one of the most important reasons for the 

 good results following. Such tillage puts the ground in very much 

 better physical condition for plant growth, aside from the more 

 favorable moisture content. There is abundant evidence also that 

 there is more available plant food in the upper layers of soil and within 

 easy reach of the plant roots. This, however, must not be interpreted 

 to mean that fertility has or has not been added to the soil. The 

 temperature and moisture conditions secured by the clean and 

 thorough cultivation given are favorable for changing the condition 

 of the plant food already in the soil so that plants may use it, while it 

 was previously in unusable form. 



Fig. 4.— a field summer-tilled by listing instead of plowing, Rawlins County, Kans-, 1909. 



One of the very important effects of summer tillage on winter 

 wheat is that it enables the wheat to start at once with a vigorous 

 growth and so enter the winter in good condition. It thus comes 

 through the winter strong, well rooted, and ready to take advantage 

 of any opportunities for growth. In this condition it is able to with- 

 stand considerable hardship, when wheat on land less thoroughly 

 prepared suffers in the winter and comes through weak or dies. It 

 will often happen that the field which was summer-tilled the preceding 

 season will contain little, if any, more moisture in the spring in the 

 first 3 feet of soil than a field which grew a crop and was plowed and 

 seeded to wheat, but the wheat on the summer-tilled land will have 

 so much better start that it will go on and make a crop under condi- 

 tions that would cause the other to fail. It appears also that grain on 

 summer-tilled land, either by virtue of better root systems or because 



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