LOSS OF SOIL WATER 



55 



Suppose we try the experiment of covering the 

 soil with some material that cannot pump water 

 readily. 



Experiment. Take four glass fruit jars, two- 

 quart size, with straight sides. If you cannot get 

 them with straight sides cut off the tops with a hot 

 iron just below the shoulder; tin pails will do if the 

 glass jars cannot be had. Fill these with moist soil 

 from the field or garden, packing it till it is as hard 

 as the unplowed or unspaded soil. Leave one of 

 them in this condition; from two of them remove 

 an inch or two of soil and replace it in the case of 

 one with clean, dry, coarse sand, and in the case of 

 the other with chaff or straw cut into half-inch 

 lengths. Stir the soil in the fourth one to a depth 

 of one inch, leaving it light and crumbly. Now 

 weigh the jars and set them aside. Weigh each 

 day for several days. The four jars illustrated in 

 Fig. 30 were prepared in this way and allowed to 

 stand seven days. In that time they lost the follow- 

 ing amounts of water : 



Amounts of water lost from jars of prepared 

 soil in seven days. 



No. i packed soil lost 5.5 oz. equal to about 75 

 tons per acre. 



No. 2 covered with straw lost 2 oz. equal to 

 about 27 tons per acre. 



No. 3 covered with dry sand lost o oz. equal to 

 about o tons per acre. 



No. 4 covered with crumbled soil lost 2.5 oz., 

 equal to about 34 tons per acre. 



