216 



SOILS AND FERTILIZERS 



each of which plats also received an application of farm ma- 

 nure at the rate of 15 tons an acre. The applications of 

 floats were at the rate of 200, 400, -800 and 2400 pounds to 

 the acre respectively. In the following table are stated the 

 increased yields over the check plats receiving the same 

 quantity of farm manure but no floats. The values of 

 the crops and cost of floats are reckoned on the same basis. 



Table 44. — Increased Yields and Values op Corn Resulting 

 from Application of Farm Manure and Floats 



It may be seen that the increase from the use of the first 

 200 pounds of floats was greater than from the additional 200 

 pounds, and from the next 400 pounds the increase was at 

 a still lower rate. This is best shown by a curve, which may 

 be seen in the upper part of Fig. 32. 



From the direction taken by the curve it may be seen that 

 finally a point will be reached when there will no longer be 

 any increase from larger applications of fertilizer. Long 

 before that point is reached, however, the use of the ferti- 

 lizer ceases to be profitable. This may be shown by another 

 diagram containing curves for the value of the grain and the 

 cost of the fertilizer. (See lower diagram in Fig. 32.) 



This diagram as well as the last column of Table 44 shows 

 that the difference between the value of the product and the 



