SOILS 



295 



Phosphorus as a Fertilizer. Fertilizers containing 

 phosphorus are barnyard manure, phosphate rock, packing 

 house wastes, and basic slag (Figure 254). 



The phosphate rock, found in many parts of the United 

 States, particularly in South Carolina, Tennessee, and 

 Florida, furnishes most of the phosphorus used in fertilizers. 



FIG. 254. Results Obtained from Using Different Fertilizers. 



Nitrogen Unfertilized 



Phosphorus 



Lime as a Fertilizer. While lime is not exactly a 

 positive plant food, it renders a valuable service to plants. 

 It is used to correct soils that have become acid, and it 

 assists in the liberation of other plant foods (Figure 255). 



How to Experiment with Fertilizer. The kind of fer- 

 tilizer that is best suited for a particular soil may be deter- 

 mined easily by experiment. A small plot of land should 

 be divided into several equal areas, or boxes may be used 

 as shown in Figure 256 ; in one box sodium nitrate may 

 be used, in another phosphate rock, in another potassium 

 nitrate, in another lime, and in still other boxes combina- 



