208 COBN CROPS 



Widstoe' states that " Fortier, working under California 

 conditions, determined that cultivation reduced the evap- 

 oration from the soil surface over 55 per cent." At the 

 Utah station similar experiments have shown that saving 

 of soil moisture by cultivation was 63 per cent for a clay, 

 34 per cent for a coarse sand, and 13 per cent for a clay 

 loam. 



EVAPORATION UNDER CORN CROP 



143. When the corn becomes large enough to shade the 

 ground, which will be soon after the time that interculture 

 begins, most of the conditions causing loss of soil moisture 

 in fallow soils will have become to a large degree ineffec- 

 tive. Wind, the most potent cause of soil drying, is 

 almost nil at the soil surface ; direct sunshine is cut off, 

 the soil being in shade part of the time ; and humidity is 

 higher! At the Nebraska station, jars of water set in 

 wheat fields level with the soil surface lost practically no 

 water. 



Another important factor in preventing loss of soil 

 water by evaporation is the spread of roots near the sur- 

 face. (See page 27.) If there is no rain, practically all 

 water moving upward from the subsoil is intercepted by 

 these roots and used by the plants. If there is rain, the 

 surface moisture is soon reduced by the surface roots to 

 a point where upward capillary movement is retarded. 



From the above, it appears that interculture of the 

 corn crop can do very little toward conserving moisture. 



THE EFFECT OF WEEDS 



144. A crop of weeds will not only take out moisture, 

 but also consume available plant food. As plant food in ' 



' WiDSTOE, John A. Dry Farming, p. 155. 



