SPECIAL FARM TOPICS 229 



surface is mellow, a spike toothed harrow will pulverize the soil 

 sufficiently. A four-horse disc harrow should be used for economy 

 of time. A man having five horses attached to a twenty-four foot 

 spike tooth harrow can put a mulch on thirty to sixty acres a day. 



When the annual rainfall drops much below twelve inches and 

 the rainfall during the growing season below five inches, it is difficult, 

 and often impossible, to raise a profitable crop. The land can be 

 fallowed one season and cropped the next, the one crop having the 

 use of what moisture can be stored from two years' rainfall. During 

 the season that no crop is raised an earth mulch must be maintained, 

 and to do this it is usually necessary to till the surface about every 

 ten days, and always after any considerable rain. In many seasons 

 paying crops may be secured by this system, where, if an attempt 

 is made to grow crops every year, the failure will be total for both 

 years. With this system the dry land farmer who has one hundred 

 and sixty acres under cultivation will each year have eighty acres in 

 crops, and eighty acres which he will have to till regularly, but 

 upon which nothing will be growing. 



Conservation of moisture is not the only benefit derived from 

 summer 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. 



Summer Tillage. One of the very important effects of sum- 

 mer 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 condi- 

 tion. It thus comes through the winter strong, well rooted, and ready 

 to take advantage of any opportunities for growth 1 . In this condition 

 it is able to withstand 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 conditions 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 of the better capillary condi- 

 tion of the soil, is able to draw water from a greater depth. Sum- 

 mer-tillage is not practicable on all soils nor for all crops. Soils 

 which are likely to blow, especially very sandy soils, can not be 

 bare tilled because they will blow away. 



