284 SYSTEMS OF PERMANENT AGRICULTURE 



sod before plowing for corn, and this application will probably be 

 repeated every six years until the total phosphorus content of the 

 plowed soil is about doubled, after which the amounts applied for 

 each rotation will be reduced to supply only about as much phos- 

 phorus as is removed in the crops grown. 



' The heavy applications of phosphorus that will thus be made 

 during the first three or four rotations cost about $1.88 per acre 

 per annum, which is less than is commonly expended for " com- 

 plete " fertilizers in the older states, in a system that supplies less 

 phosphorus than is removed in the crops grown and that thus 

 leaves the land poorer year by year. (An application of 200 

 pounds of " 2-8-2 " fertilizer l would furnish less than 9 pounds of 

 total phosphorus and at an average cost of at least $2.) 



Different systems of supplying organic matter are followed upon 

 the different plots numbered in Table 50 (legume catch crops, crop 

 residues, and farm manure), so that the same yields are not to be 

 expected upon plots 2, 3, 4, and 5, for example; but these four 

 plots differ from the next four only by the application of phos- 

 phorus to plots 6, 7, 8, and 9. For the student of details, it may be 

 said that, aside from the phosphorus applied, plot 5 is treated the 

 same as plot 6, while plots 2, 3, and 4 are treated the same as plots 

 7, 8, and 9, respectively. 



Of course, the benefits of the crop rotation, including the use of 

 different methods of supplying organic matter and nitrogen, 

 cannot be determined before even the first rotation is completed; 

 and the results thus far secured from the phosphorus applied are 

 to be considered very preliminary. They show but little of what 

 it is reasonable to expect from the system when fully under way 

 after the benefit of one or two full rotations is felt. 



In the last column of Table 50 are given the values of the in- 

 creases produced by the raw rock phosphate, including the yearly 

 totals from the three crops; that is, from three acres. By keeping 

 in mind that the annual cost of the phosphate for three acres is 

 $5-63 (while the heavy applications are being made), the financial 

 progress of the experiment during the first five years is seen at a 

 glance. In round numbers, the increase paid 50 per cent interest 



1 This means a per cent of ammonia (NHg), 8 per cent of available "phosphoric 

 acid" (PjOs), and 2 per cent of potash (K 2 O). 



