c6 THE FIRST BOOK OF FARMING 



Why did not 2, 3 and 4 lose as much water as 

 No. i? 



The soil in jar No. I was packed and water was 

 pumped to the surface by capillary force and was 

 evaporated as fast as it came to the surface. 



In No. 2 the water could rise rapidly until it 

 reached the straw, then it was stopped almost en- 

 tirely. But the straw being coarse, the air circu- 

 lated in it more or less freely and there was a slow 

 loss by evaporation. In jar No. 3 the water could 

 rise only to the sand, which was so coarse that the 

 water could not climb on it to the surface, and the 

 air circulated in the sand so slowly that there was 

 not sufficient evaporation to affect scales weighing 

 to one-quarter ounce. No. 4 lost less than No. i 

 because, as in the case of the sand, the water could 

 not climb rapidly to the surface on the coarse crumbs 

 of soil. The loss that did take place from No. 4 

 was what the air took from the loosely stirred soil 

 on the surface with a very little from the lower 

 soil. Simply stirring the surface of the soil in No. 

 4 reduced the loss of water to less than half the 

 loss from the hard soil in No. i. 



This experiment gives us the clew to the method 

 of checking loss of water from the soil by evapora- 

 tion. It is to keep the water from climbing up to 

 the surface, or check the power of the soil to pump 

 the water to the surface by making it loose on top. 

 This loose soil is called a soil mulch. Everything 

 that we do to the soil that loosens and crumbles the 

 surface tends to check the loss of water by evapora- 

 tion from the soil below. 



