THIRTY-SEVENTH ANNUAL CONVENTION. 115 



Lbs. Lbs. Lbs. 

 Nitrogen. Phosphorus. Potash. 

 Fertility returned to the soil in ma- 

 nure 93 2>7 70 



Fertility returned to the soil 



through skim-milk 18 7 7 



Total fertility returned to the 

 soil in manure and skim-milk . . 1 1 1 44 yy 



In the following table we show the amount of fertility used 

 in the manufacture of 8,000 pounds of 3.8 per cent milk and 

 the amount that we may reasonably expect to return to the soil 

 and the loss : 



Lbs. Lbs. Lbs. 



Nitrogen. Phosphorus. Potash: 



Fertility used 207 82 156 



Returned to soil in manure if skim- 

 milk is fed in 44 j j 



By subtracting we get a total loss 



of 96 38 79 



If the skim-milk is not returned 

 to the farm we get an additional 

 loss of 12 5 5 



Added to the other loss we get. .108 43 84 



Showing the total loss in fertility of the farm for each cow 

 that will produce 8,000 pounds of 3.8 per cent milk per year. 



If we had to go into the market and purchase these ele- 

 ments at commercial fertilizer prices they would cost in the 

 neighborhood of $22.00, but fortunately for the dairyman, the 

 nitrogen which costs 15 cents a pound in the market can be ob- 

 tained from the air free and there is an unlimited supply. It be- 

 comes necessary, however, for him to grow some legumes, such 



