252 SYSTEMS OF PERMANENT AGRICULTURE 



yard manure, and (3) the value of phosphorus when applied in 

 connection with manure. The first two will be further discussed 

 under the subject of farm manure. 



As an average of the results from the three series of plots, the 

 value of the increase from 320 pounds of raw phosphate was $10. 19 

 with yard manure and $10.23 with stall manure; and the value of 

 the increase from 320 pounds of acid phosphate was $11.77 with 

 yard manure and $12.01 with stall manure, the value of the ma- 

 nure alone having been deducted in all cases. If we subtract from 

 these gross gains the cost of the phosphorus, we have average net 

 profits of $9.01 for raw phosphate and $9.49 for acid phosphate; 

 or, on the basis of money invested, we have net profits of 751 per 

 cent from raw phosphate and 395 per cent from acid phosphate. 



With double the investment the profit per acre is slightly greater 

 from acid phosphate; but, on the basis of money invested, the profit 

 from raw phosphate is almost double that from acid phosphate. 



dently more or less surface wash has accumulated in this depression in times past. 

 (See the accompanying contour map of this Ohio field.) 



SECTION A 



NORTH 

 SECTION B 



SECTION C 



7 8 9 10 



13 U 15 16 W 18 19 20 11 12 13 H 15 16 17 18 19 20 11 12 13 14 16 16 17 18 19 2 



TOPOGRAPHY OF LAND: OHIO EXPERIMENT FIELD 

 One-foot contour lines; highest land at south end of section C. 



