46 Practical Farming 



tions is how much moisture can we control and retain in 

 the soil for plants during seasons of drought, for the 

 actual movement of the water in a saturated soil is of im- 

 portance mainly as a question to be determined in the drain- 

 age of land. The rapidity or slowness with which water 

 evaporates from the soil is what concerns the farmer and is 

 largely what determines the productiveness of a certain soil. 

 The Bureau of Soils of the United States 



Experiments Department of Agriculture has made some 



in Evaporation . ^ , ,. ^i ^ r 



of Moisture experiments to show the rate of evaporation 



from the different soils. In making the soil 

 surveys in various parts of the country this Bureau gave 

 various names to certain types of soil according to the lo- 

 cality where each pecuUar type of soil was seen. '^ Cecil 

 clay" has been spoken of. In like manner they call the 

 heavy clay soil of the Hagerstown valley in Maryland, 

 "Hagerstown clay." The ''Yazoo clay" is named from 

 the soil in the Yazoo river bottoms in Mississippi. These 

 three clay soils the Bureau says are the strongest types of 

 clay soil used for agricultural purposes in this country. 

 After evaporation in tin cans for twenty-five hours the 

 Cecil clay retained seven per cent, of the water it con- 

 tained at the start, while the Norfolk sand retained but 

 one per cent. In another experiment samples of a num- 

 ber of soils were exposed to the sun and wind for six 

 hours. Sand-hill soil that had lo per cent, of water at 

 first, lost 33 per cent, of its content; and Cecil clay, 

 which contained at first 17 per cent, of water, lost but 14 

 per cent, of the amount it contained. 



The importance of a loose soil cover as a preventive of 

 evaporation was shown by an experiment with various 



