2p WJIKAT SOILS OF TH1-: ALKX AXOK [ A DIVISIOX. 



Phosphoric 

 No. Nitrogen. Lime. ]\ragncsia. Potash. Oxide. 



Ih. lb. lb. lb. lb. 



1—2 1,050 r,i20 2,345 70 — 



3 — 4 1,120 — 455 S05 — 



5 — 6 — — 910 280 — 



7—^ r'575 189,420 560 315 595 



Q — 10 — 17.430 210 — — 



II — 12 — 118,860 — — 315 



13 — 14 1,190 I.61O 140 T,225 — 



T5 — 16 2,065 5,670 770 595 770 



17—18 245 210 735 245 — 



19 — 20 1,715 — — T75 r.015 



In some cases the proportions of phosphoric oxide were 

 found to Ije higher in the cultivated than in the virgin soils, but 

 the differences were so small as to be easily accountable for by 

 experimental error and the exceeding difficulty of getting a 

 virgin soil sample that would exactly correspond to the sample 

 of cultivated soil. One fact, however, stands out prominently 

 in the last table. Even if we assume, as we may 

 fairly do, that the difference in lime content between 

 the virgin and cultivated soils may be largely due to 

 une(|ual distribution of lime in the soil, and therefore 

 that the lime in the cultivated soil is more evenly distributed 

 tlian in the virgin samples which may have been taken from spots 

 i)articularly rich in lime, it still remains clear that successive crops 

 have depleted the soil of relatively large quantities of nitrogen 

 F.nd lime, but of comparatively small amounts of potash, and 

 still less of ])hosphates. The explanation seems clear that lime 

 and nitrogen were present in abundance, and so the stocks on 

 v,hich to draw were large ; but there was very little potash, and 

 >till less of phosphatic material to draw on, and so the crops 

 were soon straitened for lack of these latter. 



A few calculations may serve to enforce this point. A wheat 

 crop of 30 bushels per acre removes from an acre of soil the 

 following* : — 



lb. 



Xitrcigen 48.0 



Lime 9.2 



Ahignesia 7.1 



Potash 28.8 



Phosphoric ( )xide 21. i 



Ihat is to say, an ordinary wheat crop requires, roughly. 

 half as nuich potash or phosphoric oxide as nitrogen, or from 

 two to three times more i)otash or phosphoric oxide than lime. 

 In the .Mexandria soils examined, the process has been reversed, 

 and far more of nitrogen and lime have gone than of potash 

 and phosjihoric oxide ; it is more than possible that the entire 



* Cameron and Aikman : " Johnston's Elements of Agricultural 

 Chemistry." i9tli cd., 278-9. 



