1j4 I^'ood lOi; 1*1. A NTS. 



Tliiis a carcrtil I'ccoi'd is kcpl of llif aiiioiiiil (tf iiilro- 

 li'cii applied cacli ycai' and of llic yield ol' dvy mailer 

 I'l-oiii each cylinder. H'roiii tleterniiiiatious of the ainouiit 

 of iiitr()i»'oii in the dry mailer llie total amoiiid of inti'o- 

 U'eii remove(l by the crop each year is easily calculatecl. 



Yield of Dry Matter. 



The yield of dry matter under the four different treat- 

 ments for the 20 years is' shown in tahle 1, averages be- 

 ini>' s^iven for two lO-year periods and ;dso for the entire 

 20 years. Foi' each 10-vear period the yield has been 

 largest with the manure, though it is less for the second 

 lO-year ])eri()d than foi- the first, which would indicate 

 that with manure at the rate of 16 tons i)er acre the 

 fei-tility of the soil is not being fully maintained. The 

 lowest yield is from ISB where dried blood is used as 

 the source of nitrogen. Here again the average yield is 

 less for the second 10-year period than for the first. For 

 plots 8B and 17B, which receiye nitrate of soda and 

 annuonium sulfate, respectiyely, the average yields for 

 the first 10 years are essentially the same for the two 

 treatments, but for the second 10 years the average for 

 the nitrate of soda treatment is considerably above that 

 foi- the ammonium sulfate; furthermore, the average 

 yield with ammonium sulfate is, like the yield with dried 

 blood and farm manure, less for the second than for the 

 first 10-year period. With the nitrate of soda, however, 

 the figures are reversed, that is the average yield for 

 the second 10 years is somewhat above that for the first 

 10 years. 



The (luestion may well be raised as to why the average 

 yields on 4I>, 17I> and 18B should be less for the second 

 10-year period than for the first, while the yield on 8B 

 has been well maintained for the 20 years. Since phos- 

 phoric acid and potash have been supplied each year in 

 liberal amounts, and lime has been used at stated inter- 

 \als, it would seem clear that the falling off in yield 

 must be due to a deliciency of available nitrogen, not- 

 willistanding the fad that cylinders 17B and 1813 receive 



