54 



THE FIRST BOOK OF FARMING 



We learned that roots take water from the soil 

 for the use of the plant and send it up to the leaves, 

 which in turn send it out into the air, or transpire 

 it, as this process is called. We learned also that 

 the amount transpired is very great. Now water 

 that is pumped up and transpired by the crops we 

 are growing we consider properly used. But when 

 weeds grow with the crop and pump and transpire 

 water we consider this water as lost or wasted. 



Water may be lost then by being pumped up and 

 transpired by weeds. And this is the way weeds do 

 their greatest injury to crops during dry weather. 

 The remedy is easily pointed out. Kill the weeds 

 or do not let them get a start. 



There is another way, which we are not apt to 

 notice, by which water may be lost from the soil. 

 When the soil in the pans in a previous experiment 

 (page 26) had been wet and set aside a few days 

 it became very dry. How did the water get out 

 of this soil? That at the surface of the soil evap- 

 orated or was changed into vapor and passed into 

 the air. Then water from below the surface was 

 pumped up by capillary force to take its place just 

 as the water was pumped up in the tubes of soil. 

 This in turn was evaporated and the process re- 

 peated till all of the water in the soil had passed 

 into the air. Now this process is going on in the 

 field whenever it is not raining or the ground is 

 not frozen very hard. 



Water then may be lost by evaporation. 



How can we check this loss? 



