SOIL WATEK, DBAINAGE, AND IKKIGATION 207 



Professor King says that during the growing season, in 

 producing a ton of clover hay, which after drying is 85% 

 dry matter, 375 tons of water are carried into the air either 

 through the plant or by evaporation directly from the soil. 

 There may often be a yield of more than 2 tons of clover hay 

 to the acre, but assuming it to be 2 tons, the amount of 

 water taken from the soil to make the crop is equal to more 

 than 6 inches of rainfall. It is estimated that a rainfall of 

 almost 10 inches is used in producing a crop of corn of 50 

 bushels per acre. What amount of rainfall is there in your 

 locality during the growing season ? 



229. Soil water as affected by tillage. The ways in which 

 farm and garden soils are cultivated has much to do with 

 their water-holding capacity. When water evaporates from 

 the surface of compact soils, the water from below, if there is 

 any, immediately comes to the surface. Water passes readily 

 through relatively solid soils. 



If an extremely fine-drawn glass tube is placed with one 

 end in a dish of water, the water will rise some distance in 

 the tube. This is known as capillarity. The fine spaces be- 

 tween the walls of the soil particles act as capillary tubes, 

 and the soil water passes upward if the soil is compact so 

 that spaces are continuous. 



The action of the soil may be illustrated by use of a piece 

 of compressed sugar. Touch one end of the lump to a liquid 

 and the liquid soon goes through the entire lump. In the same 

 way in dry weather compact soils lose their deep soil water 

 through evaporation. Another experiment with two lumps of 

 sugar will suggest a method of cultivating soils so as to hold 

 moisture. Allow a second lump to lie loosely upon the first, 

 which just touches the liquid, and the liquid will pass into 

 the second very slowly if at all. The so-called capillary con- 

 nections within the lumps of sugar are not continuous between 

 the two ; there are no continuous lines along which the water 

 passes- In the same way constant surface cultivation of the 



