890 Mdrht-flardni Soils and rrops^ 



In tlie case of the dark sands we have the following variations for 

 two samples taken : 



KgO varies between -lli— JS 



P2O5 „ -ii-ig 



CaCOs „ -08-09 



re^Og, AloOg „ 8-70-8-79 



Coarse sand „ 54-6-57'2 



The dark sand seems to be differentiated from the brown sands by 

 a much lower content of potash and phosphoric acid. 



To take one more example, the Oxford clay soils may be considered. 

 The Oxford clay formation has been divided into two soil formations 

 (a) pure clay soils, (6) clay loams. 



Class {a) is characterized by the following: 



Coarse sand 14-8 



Clay 29-5 



CaCO:, -12 



K2O 1-18 



I'aOg -09 



Fe^Og, AI2O3 15-4 



Class (h) had the following variations in three samples analysed: 



Coarse sand varies between 20-0-23-3 



Clay „ 19-7-21-2 



CaCOg „ -06-70 



KoO ., -74-76 



P2O5 „ -08-19* 



FegOg, AI2O3 „ 10-30-11-52 



The results of chemical analysis are sufficient to distinguish the 

 Oxford clay series from all the other clay formations dealt witli in this 

 paper, for the percentage of calcium carbonate and phosphoric acid is 

 extremely low in all the samples taken from this series. 



Again mechanical analysis at once reveals the necessity for a 

 sub-division into two soil formations, since there is a constant difference 

 of 9 per cent, in the percentage of clay found in the two soil formations 

 mapped from field observations. 



The following table shows the average of analyses of soils on each 

 soil formation in terms of mechanical and chemical analysis. 



* The sample containiiiji •!!> per cent. Iiiui -(l-i;) piT cent, more available P^Dj than 

 any other soil in this formation and it is jirobable that this has been added in manures. 



