63 



CalculiiU' llie tiital miniheT oi pcjuiid.s of watei' rctaiiicil jx'f culiic fciol of <lr}- yoil 

 and al^■<l the number of surface inches of water it represents. 



This experiment ilhistrates the power of different types of loose scjil to retain 

 water. One of the advantages of cultivating soil is to make it loose in structure so 

 that rain will ])e absorlx'd and retained more thoroughly than would he the case if 

 the soil were uncultivated. Study results from this experiment in connecti<jn with 

 those of experiment No. 4 for compact soil. 



Exper'nnctit No. ■}■ 



THE roWKIt OF COMPACT SOILS 'J'O liETAlN MOlS'rUKE. 



Use soils Nos. 2, ?>, 4, and 5 in this exi)eriment. Place disks of moist cheese cloth 

 in the bottom (jf the tubes (fig. 13). Weigh and then till within 1 inch of the top 

 in the following mannner: Pour in 1 measure of soil. Place cylinder in comi)acting 

 machine and drop weight six times from the 12-inch mark. Pour in another meas- 

 ure and repeat. Continue tliis until cylinder is filled within 1 inch of the top. 



Fig. 13. — Determining the power ol soils to retain moisture. 



Place the lillcd tubes in the empty galvanized iron liox. Pour water in the liox 

 until the water level almost reaches the tops of the tu))es, thus allowing the water to 

 percf>late up through the soils. When the water level in the tubes comes u]> to the 

 level of the water in the ]>ox remove the tubes and place them in the frame where 

 the water is allowed to jjercolate out of them. (ila--s plates should lie ])lac('<l over 

 the tops of the tuljes to jirevent evaporation. The tubes should lie weiglicd from 

 day to day until the mininunu weight is reache<l — imtil jiercolation ceases. 



The difference in weiglit between the tubes filled with dry soil and the wet soil will 

 ])e the amount of water retained by the compact soil. In order to get the total water 

 content of the wet soil it will be necessary to add to this the weight of hygroscopic 

 water which the dry soil contained. The hygroscopic water of the dry soil should 

 be determined with a special sample at the time the tubes are filled. 



Calculate the total number of pounds of water retained per cubic foot of dry soil 

 and also the number of surface inches of water it represents. 



This experiment illustrates the power of different types of compact soil to retain 

 ■water. 



The results of this experiment should be studied in coiiin'ction with those of 

 experiment No. 3. 



