120 MAN ON THE LANDSCAPE 



feet so that they strike the soil. Examine the paper. Do the shattered 

 drops carry soil with them ? How far does the splash extend ? 



(2) Repeat, placing both soil and a new paper at a sharp angle 

 with the floor, simulating a sloping field. Smooth over the soil before 

 releasing the water this second time. Do not permit every drop to 

 strike the same spot or a hole will be dug; this is not what happens 

 during a rain, although such digging demonstrates the hydraulic 

 power of a stream of water. (Do not expect much more than half the 

 splash to fall downhill. The difference is small, but remember the 

 cumulative effect of years of rainfall in this work). Examine the 

 paper for evidence of total average soil movement. Is it downhill ? 



How do you account for the fact that streams, draining what 

 appear to be level farmlands, run muddy after rains ? 



How do you account for the fact that many gently rounded hill- 

 tops of old, dissected plateaus (such as the Piedmont, Ozark, and 

 Appalachian) are severely and more or less uniformly eroded, while 

 the surrounding steep hillsides are perhaps not? As a hint, what use 

 is made of the two types of terrain? (Are there trees on the steep 

 slopes?) Might the same thing happen on rolling prairie or plain? 



(3) Place a section of sod covered soil in the container and try 

 the experiment a third time. Do the shattered drops carry soil ? Does 

 the splash extend as far as in the case of bare soil ? 



(4) Now, although the average teacher is already fed up with the 

 inconvenience of setting up such demonstrations, let us, for the bene- 

 fit of the exceptional teacher, go on. In order to show clearly the very 

 important function of surface litter in preserving a good soil, we shall 

 need two similar shallow boxes or biscuit pans, a sprinkling can or a 

 tin can with a dozen nail holes punched in the bottom, and enough 

 good loam soil to completely fill the boxes. This good loam must have 

 a granular structure. Needed also is enough straw, grass clippings, 

 hay, leaves or other mulching material to cover one box so that rain- 

 drops will not strike bare soil. Do not cover it yet. 



To proceed, drop the artificial rain on the box of bare soil. Try, 

 say, one half inch of rain, evenly distributed (this can be calculated 

 from the area of the box and the fact that there are 231 cu. in. per 

 gallon of water). Observe carefully any changes which occur in the 

 surface soil structure. Are the granules or aggregates broken down? 

 Does the soil surface seal? Compare with the dry box. Does the 

 water infiltrate rapidly at first later? 



Now cover the second box with a surface mulch. Drop the water. 

 Does it infiltrate better ? When the rain is over, carefully remove the 

 litter without disturbing the soil. Compare the two surfaces. On 

 sloping land, which condition would discourage erosion ? Which con- 

 dition would admit air to the soil most freely and continuously? 

 Which would require the most cultivation ? Why ? What would you 

 recommend in regard to the practice of removing all possible crop 

 remains from fields? What would you recommend .in regard to burn- 

 ing off weeds from the fields and leaf litter from woodlots? What 



