WHEAT SOILS OK Till-: ALEXANDRIA DIVISION. JT,\ 



loss is not due to wheat, hut it is equally certain that in most 

 of the soils analysed the distrihution of the several i)lant-food 

 constituents is by no means co-ordinated to the retjuirements oi 

 wheat crops. We may put this in another way. Excluding Nos. 

 8 and 12, which were evidently taken from hi^^hlv calcareous 

 spots, the average composition of the remainin<; ei,t;ht virgin 

 soils, Nos. _>, 4. 6, 10, 14, 16, 18 and 20, is as follows:— 



Nitrogen 112 i)er cent. 



Lime 249 



Magnesia ni 



Potash ogo 



Phosphoric Oxide 042 „ 



Such an average soil would ctMitain the following weights of 

 these plant- food constituents in an acre,* one foot deep: — 



Nitrogen 3-9^0 lb. 



Lime *%7i5 Ih. 



Magnesia 3«885 lb. 



Potash 3,150 lb. 



Phos])horic Oxide i,470 lb. 



Roughly, therefore, there would be enough nitrogen, in such 

 an average soil, for 80 crops of wheat, lime for nearly 

 1. 000 crops, magnesia for 560, potash for about no, and phos- 

 phoric oxide for only 69. f At the same time, as was pointed 

 out by me many years ago,;i: the crops cannot by any ])ossibility 

 extract all the i)hosphoric oxide to the last grain within one 

 foot depth of soil, and so, long before the 69 years have elapsed. 



the soil will have become hopelessly barren and unproductivej, and 

 as the fertility of the soil diminishes year by year the crops will become 

 poorer and poorer, until at length a stage is reached when it will cease 

 to be worth while cultivating the land at all-§ 



Now it must be remembered that the above type represents 

 an average I'irgiu soil of the Alexandria Division, as yet un- 

 exhausted by cultivation ; and many of the soils of this type 

 have now been under cultivation for many years — and that 

 without manure ; small wonder then that they can no longer 

 grow wheat. 



A similar process of calculation may be applied to the soils 

 that ha\e been throtigh the exhausting process of continuous 

 cultivation without manure, and so the following table is arrived 

 at, showing (a) the quantities, (in pounds per acre to a depth 

 of twelve inches) of the various ])lant-food constituents remain- 

 mg in the soil, and {h) the number of wheat crops that would 



* Taking the weight of an acre foot of loam at .si million p.nmds. 

 tC-Y Hopkin's "Soil Fertilitv and Permanent Agriculture," 74- 

 JC.G.H. Dept. of .-Xor. .Senior Analvst's Report (uSga), 14. 

 § See also CG.H. Dept. of Agr. Senior Analyst's Report (1894), 2\- 



