156 AGRONOMY 



vegetation overpower those which grew in the water, cliffs 

 weather to soil and a different flora comes in. In fields allowed 

 to lie fallow the plant covering changes little by little for 

 years, and in the waste places there is always more or less 

 succession of one group of plants by another. In parts of our 

 country there has also been a steady migration of trees into 

 the prairie region since the glacial period, and the movement 

 is still going on. 



PRACTICAL EXERCISES 



1. Visit the nearest hardware or implement store and examine the 

 machines used in tilling the soil. Make a list of the kinds seen and 

 the uses to which they are put. 



2. After a rain mark off 3 sq. yd. in the open ground. Cover 1 sq. yd. 

 with a mulch of leaves or stable manure, pulverize the top layer of 

 soil in the second, and let the third go untouched. At the end of a 

 week examine as to moisture content in the upper layers. 



3. In England it has been estimated that there are 53,767 earth- 

 worms to the acre. Find the average number of worms to the square 

 foot in the school garden by examining three different spots, and 

 estimate the number to the acre upon this basis. How does your own 

 locality compare with England in this respect? 



4. Find out from the farmers near by what the common crop rota- 

 tions of the region are. Are there any fields in which rotation is not 

 practiced? If so, how do present crops compare with former crops? 



5. Make a table of the crop rotations practiced in your county. 



References 



Hopkins, " Soil Fertility and Permanent Agriculture." 

 King, " The Soil." 



Farmers 1 Bulletins 



245. Renovating Worn-out Soils. 



327. Conservation of Natural Resources. 



342. Conservation of Soil Resources. 



