102 



SOILS AND FERTILIZERS 



1000 Pounds 

 BARN YARD MANUFu 



If 800 pounds of Virginia leaf tobacco are raised and 

 removed from an acre of land, the main elements re- 

 moved are as indicated in Figure 37 : 



Nitrogenous 43.7 

 Phosphoric 5.0 

 Potassic 57.3 



Average barnyard manure contains to each 1000 

 pounds 5 pounds of nitrogenous, 3 pounds of phosphoric, 

 and 6 pounds of potassic plant food as shown in 

 Figure 38. 



It is evident that if the fertility of the soil removed by 

 the 800 pounds of tobacco is to be restored by the appli- 

 cation of manure, there 

 must be applied more than 

 8000 pounds an acre to re- 

 plenish the nitrogenous food 

 or more than 9000 pounds 

 to restore the potassic ele- 

 ment. In either case there 

 would be more of the phos- 

 phoric supplied in the ma- 

 nure than would be required 

 by the tobacco. This would, 

 of course, do no harm, but 

 fertilizers containing a larger 

 proportion of nitrogen and 

 of potassium might be ob- 

 tained at a lower cost than 

 the large quantity of manure required. 



In many cases the easiest and best way to obtain a 

 supply of nitrogen for crops is by growing leguminous 

 plants, such as clover, alfalfa, peas, and beans. These 



in- 

 o'- 

 er 



z. 



LU. 

 ID-. 

 O 



a:'. 



h- 



FIG. 38. Showing the Number of 

 Pounds of Plant Food in 1000 

 Pounds of Barnyard Manure. 



