Rural School Leaflet. 989 



of the column. Last month it was noted that the soil will hold a large 

 amount of water and that this water percolates most rapidly through 

 the coarsest soil, that is, the one having the largest pores. The water 

 which is held i,n these pores is called capillary, or film water. This month 

 we shall observe the capillary movement of water which is the manner 

 in which moisture is supplied to plants. 



Take enough of your coarsest and finest soil to fill two lamp chim- 

 neys with each. Fill the chimneys to within one inch of the top in the 

 same way as before by tying a piece of muslin over the lower end. Set 

 each chimney in a shallow dish (individual dessert dishes) each con- 

 taining the same amount of water — just full enough so that the water 

 will not flow over the edge when the chimney is inserted. Observe the 

 water pass up through the soil column. Note in which it moves most 

 rapidly. Note also how different layers of soil affect the water. Observe 

 how long it takes water to reach the top in each chimney. Add more 

 water to the dishes when necessary and keep account of this amount. 

 Note which chimney has used the most water by the time moisture 

 reaches the top. Consider also whether, if your soil columns were two 

 or three feet tall, the water would move to the top at the same rate 

 as you observe in the chimneys. The water will move most readily 

 if the soil is very slightly damp at the outset. It climbs from particle 

 to particle in the soil and on a level may move a long distance, but in 

 moving upward it is hindered by the pull of the earth, so that 

 it may not move to an indefinite height. In the field, water moves up 

 from the deep sub-soil, where the pores are filled, to meet the needs of 

 the plant roots. The soil which is best able to move water fast enough 

 to meet the needs of the plant will produce the best crops as a rule. 

 Although the soil be not saturated, if it is more moist in one place than 

 in another water will move to the dryer part. 



At the surface, evaporation occurs and the loss in this way may be 

 so great as to injure the plants which are growing. If you will let your 

 soils stand for a few days you will get some idea of how much water 

 may be lost in this way. This can be largely avoided. After you have 

 found how fast water evaporates from your soils fill the top of one 

 chimney of each soil with the best dry sand you have. Fill the other 

 chimney with dry leaves or cut straw and let all stand for a few days 

 more. Is the rate of loss as rapid? Does the straw have any more 

 effect than the soil? Such a dry layer placed on the wet soil to prevent 

 evaporation is called a mulch, and when it consists of soil it may be 

 called a dust mulch or a "dust blanket," because it holds moisture in 

 the soil. In the field the mulch may be formed by cultivation to keep 



