56 Report <>k the Department of Agronomy of the 



mixed with each ton of manure. The comparison is made on fresh 

 stall-manure and weathered yard-manure separately. The average 

 annual yields per acre for the three crops for this length of time are 

 given below: 



It is to be noticed that in this comparison of equal weights of acid 

 phosphate and rock phosphate the two have given almost identically 

 the same yields. But the acid phosphate has cost nearly double 

 that of the rock phosphate and the question naturally arises what 

 would have been the result of applying rock phosphate to the same 

 money's worth as acid phosphate. Then, too, even in the amounts 

 used the natural product is supplying the soil twice as much phos- 

 phorus as the acid material, and must mean something for the future. 



A good way to apply rock phosphate is at the rate of 1000 to 2000 

 pounds per acre once in a three- to six-year rotation, plowing it under 

 with a clover or alfalfa sod, or with an application of manure, or 

 with both sod and manure. In the three examples cited above from 

 Illinois the phosphorus used has been natural rock phosphate and 

 it has been plowed under with the clover sod once in a rotation. 

 At New York State prices for rock phosphate an application of 1000 

 pounds per acre once in 3 years would be an expense of about $1.50 

 per acre per year. 



The practice of using the natural phosphate in liberal quantities 

 appeals to the farmer who has an understanding of the principles 

 of soil fertility and who views his business in a large way, looking 

 not only to the profits of the present season but also to the net returns 

 over a period of years. 



home mixing of fertilizers. 



Some truck and some fruit crops, tobacco, and a few others require 

 relatively larger amounts of nitrogen and potassium than general 

 farm crops. Also these crops usually have a much higher value 

 per acre. It may, therefore, often be profitable to use liberal amounts 



