EXERCISE A-5. TO STUDY THE RELATIVE PRODUC- 

 TIVENESS OF SOIL AND SUBSOIL. 



Equipment: Two flower pots or quart cans; wheat 

 seed; soil and subsoil from the same place. 



Method : Fill one pot with moist surface soil, the other 

 with moist subsoil, and plant six grains of wheat in each. 

 Keep the pots watered and compare the growth of plants 

 from time to time. 



Discussion: Why are washed hillsides and the high 

 points in the fields usually less productive than the level 

 land and the lower levels? Steep land should be cultivated 

 across the slopes and should be kept covered w^ith some 

 crop in order to prevent the washing away of the surface 

 soil. Deep plowing is often desirable to increase the depth 

 of the surface soil. If the soil has always been plowed 

 shallow it will be better to plov/ only an inch or two deeper 

 each year until the desired depth is reached, than to plow 

 deep the first year. Why? Observe the growth of corn 

 or wheat in the " dead furrow " between the lands. 



While the plowing up of the subsoil in the humid regions 

 frequently results in a decreased productiveness, the soil 

 and the deeper layers in the arid regions may be mixcnl 

 without injury. In these dry sections good crops are fr(^- 

 quently grown where the top soil has been entirely removed 

 in the preparation of the land foi' irrigation. 



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