u 



ELEMENTS OF FARM PRACTICE 



2. How many pounds of com are produced on an acre yielding 

 40 bus.? (A bu. of shelled com weighs 56 lbs.) 



3. How many pounds of potatoes are produced on an acre yield- 

 ing 150 bu.? (A bu. of potatoes weighs 60 lbs.) 



AVAILABLE PLANT FOOD 



Amotmt of Plant Food. — Most soils contain enough 

 plant food to grow crops for many years, several hundred 

 perhaps, but this plant food is not present in the soil in 

 a soluble form and it is well it is not. If it were soluble 

 it would be dissolved by the water during a heavy rain, 

 and as the water flowed off over the fields and into the 

 river it would carry with it the plant food, thus leaving 

 the soil unproductive. This may be better understood if 

 one takes two glasses of water, puts a spoonful of sand 

 into one and a spoonful of sugar into the other, and stirs. 

 Then carefully pour the water out of both glasses. The 

 sugar being soluble has been dissolved and will pass out 



Figure 6. — (1) A piece of sod showing the grass roots. (2) A lump of earth taken 

 from a field that has grown corn continuously for fourteen years and which ia 

 badly depleted of vegetable matter. 



