270 



SYSTEMS OF PERMANENT AGRICULTURE 



A study of Table 44 shows a decrease in ear corn and a small 

 increase in corn stover from the use of raw calcium phosphate the 

 first year, and some increase in both oats and oat straw the second 

 year. During the next four years this raw rock phosphate produced 

 a larger average increase in the yield of hay than any other form of 

 phosphorus applied, except steamed bone meal. This suggests 

 that the longer growing biennial and perennial plants, such as clover 

 and timothy, may be better able to utilize the raw phosphate than 

 the short-lived annuals. 



It is important to keep in mind also that these four years con- 

 stitute a considerable part of the entire time of the experiment, 

 and that it was only during these four years that the investigations 

 have the greatest practical significance, because the first two years 

 would be required to get the phosphates thoroughly incorporated 

 with the soil and get well under way the action of the various 

 agencies that help to make the raw phosphates available, and it 

 was only during the first six years that equal money values of the 

 different phosphates were used. As stated by the Rhode Island 

 Station, " Dehe"rain and other French writers recommend that, 

 upon acid soils, such untreated phosphates should be applied 

 several months or a year before liming is resorted to, so as to secure 

 as great a decomposing action upon them by the soil as possible." 



In 1900, the three largest yields of ear corn were produced by 

 steamed bone meal, raw calcium phosphate, and roasted aluminum 

 phosphate, in the order named. 



The results from the several crops grown in 1901 are reported 

 as the weight of the fresh or green crops. It will be seen that the 

 raw calcium phosphate produced some increase in eleven of the 

 twelve crops reported, and the average increase from this raw rock 

 phosphate is more than three fourths as much as from the common 

 acid phosphate costing two or three times as much for the appli- 

 cations made previous to 1901. 



The relative effects of the different phosphates are about the 

 same on the unlimed land as where some lime had been applied, 

 except that the superiority of the slag phosphate, steamed bone 

 meal, and common raw rock phosphate (calcium phosphate) over 

 the four acid phosphates (including superphosphate) was even 

 more marked in the four years' hay crops on the unlimed land. 



