276 SYSTEMS OF PERMANENT AGRICULTURE 



fine-ground South Carolina raw rock phosphate; and, for soluble 

 phosphorus, 400 pounds of acidulated bone black were used for 

 1886, 1887, and 1889, and 500 pounds of acid phosphate made from 

 South Carolina rock for 1893 and 1894. The stable manure was 

 applied five times at the rate of 20 tons per acre. The results are 

 reported in Table 46 for each of the eight crops harvested. 



TABLE 46. MAINE EXPERIMENTS WITH .DIFFERENT PHOSPHATES 

 Pounds per Acre of Air-dry Produce: Average of Three Plots in Each Case 



Of the different forms of phosphorus, the acid phosphate gave the 

 best results for the first two years, especially in oat straw, but 

 afterward the bone meal gave the best results. The raw phosphate 

 produced only about one half as much increase as the other forms, 

 but at less than one third the cost. 



