96 



FIRST YEAR SCIENCE 



46. Soil Water. Although many soils contain every 

 thing needful for the production of agricultural plants, 

 yet the rainfall is insufficient or so unevenly distributed 

 that these plants are unable to grow. This is true over a 

 large area of the United States, and the same conditions 

 often prevail' over the usually well watered part of the 

 country in times of drought. The question of increasing 

 the water-holding capacity and of preventing the loss of 

 water by evaporation or in other ways is a very important 

 one. 



Experiment 52. Weigh out equal amounts (about 100 g. each) of 

 dried gravel, coarse sand and very fine sand. Put each of these into 

 a four -inch funnel which has been fitted with a filter paper. Pour 

 water upon each until all that can be absorbed has been absorbed. 

 Allow each to stand until water ceases to drop from the funnel. 

 Weigh again, balancing the weight of the wet filter paper retainer by 

 a similar wet filter paper placed on the weight side of the scales. Which 

 of these substances is capable of holding the most water ? Since 



water does not penetrate 

 into the grains composing 

 these different substances 

 the difference in water hold- 

 ing capacity must be due to 

 the different sizes of the 

 grains. 



If we dig deep enough 

 into almost any soil we 

 shall find water. Wells 

 show this. Certain trees 

 arid plants have such 

 long roots that they can 

 reach the underlying 

 water and flourish where 

 other plants will die. When wet lands are so drained 

 by tiling that the plants can send their long roots down 



ALFALFA ROOT. 



A long root which has gone deep to seek 

 water. 



