Dry Farming and Irrigation 157 



teen million stomata, out of which water vapor escapes, 

 and that a sunflower as tall as a man may, by transpira- 

 tion, lose as much as a quart of water in a day. It 

 has been found that at least ten inches of rainfall is How much 

 necessary in most places to produce even a fair crop, ^ewssary 

 However, the amount necessary is different in different 

 places, for loss by evaporation from the soil will be much 

 greater where there is much wind and hot weather than 

 where there is less wind and a cooler temperature. The 

 soil, too, must be deep enough to absorb all the rain that Depth of 

 does fall. The depth down to bedrock should be at S0lt 

 least five or six feet. 



The practices which, taken together, make the system Methods 

 called " dry farming," are all for the purpose of making 

 a light rainfall go as far as possible toward producing 

 a good crop. They are of use in gardening as well as 

 in growing field crops. 



In dry regions where there is summer rainfall, the Summer 

 ground should be plowed as soon as a crop is harvested. P^ wm s 

 (For the practice where there is little or no rain in summer, The advan- 

 see page 160.) The plowed ground will absorb any rain ^^ 

 that falls instead of allowing it to run off. The deeper deep as well 

 the plowing, the larger will be the reservoir of moisture 

 for use by the next crop. Tests made with fall wheat 

 during seven years at the Kansas Agricultural Experi- 

 ment Station, Manhattan, Kansas, show clearly the 

 advantage in plowing deep and early. The fields used 

 for the tests were similar. The different yields per acre 

 were due to the different preparation of the seed bed in 

 each case. The results (averaged for the years 1911 

 to 1917) were as follows: 



