PLANT FEEDING. 33 



Live Stock and the Soil. Having solved these prob- 

 lems, you have discovered what a large amount of 

 expensive plant food is taken from the soil each year by 

 the corn crop. This must be replaced in some way or the 

 land will lose its fertility and become "worn out." If the 

 corn is sold each year, a large amount of fertilizer must 

 be bought. However, suppose the farmer keeps the corn 

 he raises and feeds it to his stock. Let us see what the 

 results are then. The farmer may keep cows and sell 

 the butter, keeping the skim milk to feed calves and to 

 fatten hogs. When butter is sold very little of the ele- 

 ments of the plant food that we have talked about nitro- 

 gen, phosphorus and potassium is removed. The cows 

 can live upon what is raised on the farm, and most of the 

 elements of plant food in the food consumed by the ani- 

 mals are returned to the soil in the manure. Butter con- 

 tains only 0.125% of nitrogen, 0.188% of phosphoric 

 acid and 0.031% of potash. 



Let us suppose, also, that a number of hogs are kept. 

 They can be fed when young upon the skim milk and 

 fattened with some of the corn that is grown on the 

 farm. With the hogs, as with the cows, a large part of 

 the nitrogen and other elements is returned to the 

 soil in the manure. The carcass of the hog averages 

 about 2% nitrogen, 8.1% phosphoric acid, and 0.16% 

 potash. 



Using the percentages given above, work out the fol- 

 lowing problems, comparing with the results you obtained 

 on the corn problems. Which is the more economical 

 method of farming to sell the corn or to feed it, selling 

 only the animal products? 



QUESTIONS. 



1. How many ounces of nitrogen are contained in a 

 pound of butter? How many ounces of phosphoric acid? 

 Of potash? 



