558 IOWA DEPARTMENT OF AGRICULTURE 



DRAINAGE WARMS THE SOIL. 



Observation and experiment have shown that the drained soil is, on an 

 average, from 6 to 10 degrees warmer at seven inches below the surface 

 than an undrained soil. If the water had been left to evaporate from the 

 surface this heat would have been taken in changing the water into 

 vapor. This difference in temperature represents a season in which 

 spring conies probably two or three weeks earlier. 



DRAINAGE MAKES THE SOIL MELLOW. 



When the water is drained out of the soil the air enters and the ground 

 slacks and shrinks and by chemical action with the air soon becomes 

 mellow and porous. 



DRAINAGE DEEPENS THE SOIL. 



By lowering the water level and making the soil mellow the roots go 

 deeper and the subsoil is changed and made good for the roots to seek 

 in for nourishment. 



DRAINAGE PROTECTS AGAINST DROUTH. 



Some have feared that the water taken away by the tile will be needed 

 when a dry time comes. Lands which suffer most by drouth are most 

 benefited by drainage. The deepened soil permits the roots to go deep be- 

 low the influence of the sun's rays. Mellow soil retains moisture much 

 better than hard baked soil. This principle is the basis of the Campbell 

 system of dry farming practiced in the arid regions of the West and South- 

 west, where the conservation of moisture is so essential to successful 

 agriculture. 



DRAINAGE LENGTHENS SEASON. 



Drainage lengthens the season at both ends. 



Tile drains work in winter and early spring and dry the soil early. It 

 warms the soil. Planting can be done earlier. George Judd, of Springfield, 

 111., who has tiled much, said: "My land is planted in corn while land 

 across the road of the same character, but not tiled, is too wet to plow." 



There is less danger from early frosts. Prof. Webber, of the Cham- 

 paign (111.) sugar works, said that none of the cane grown on tile drained 

 land had been the least injured by frost, while that on undrained land 

 had been more or less damaged and some of it very badly. 



DRAINAGE PREVENTS SURFACE WASHING. 



Drainage prevents surface washing by taking the water away under the 

 surface. The rain sinks readily into the soil made mellow by drainage. 



INCREASES FERTILITY. 



Drainage increases fertility "by preventing the soil from becoming cold 

 and sour; by admitting air and such gases as carbonic acid, nitric acid 

 and ammonia, which aids disintegration of mineral and organic matter and 

 fits them for plant food. 



