324 H(3\V LONG DOES LLVIE LAST IN THE SOIL ? [SEPT., 



nary operations of cultivation. The soils of the various 

 Rothamsted experimental fields are of similar origin and 

 character, and consist of a reddish heavy loam or sandy clay 

 containing a large but variable proportion of unworn flints with 

 a few pebbles. The amount of carbonate of lime present is 

 very small, less than one-fiRh of i per cent., except in the sur- 

 face layer, where from 2 to 5 per cent, is met with, disseminated 

 through the soil in rounded grains of all sizes up to one-eighth 

 of an inch in diameter. That this carbonate of lime is of arti- 

 ficial origin may be gathered from the following reasons : — 

 (i) Its amount varies greatly from field to field, though the pro- 

 portion in the subsoil below nine inches is much the same every- 

 where. (2) The Rothamsted fields lie at the highest level of 

 a plateau ; there are no higher lands near from which a chalky 

 surface soil might have been washed. (3) On some of the fields 

 the chalking process seems to have been omitted ; the surface 

 soil contains no more carbonate of lime than the subsoil. This 

 again is the case with the soil of the adjoining Harpenden 

 Common, land which has certainly never been under cultiva- 

 tion. 



The following table will illustrate these points : — 



PERCENTAGE OF CARBONATE OF LLME IN FINE DRY SOIL. 





Broad- 

 balk 

 wheat. 



Hoos 

 barley. 



Agdell 

 rotation. 



Little 

 Hoos. 



Harpen- 

 den 

 Common. 



(iees- 

 croft. 



1st depth of 9 in. 

 2nd depth of 9 in. 



0'12 



2-3 



O"20 



0-17 



27 



0"I2 



0-2I 

 0-14 



o-i6 

 0-13 



The samples in question were all taken from unmanured 

 plots in 1904-5 ; lower depths show practically the same con- 

 tent of carbonate of lime as the second depth. 



From some of the Rothamsted plots samples of soil that 

 were taken as far back as 1865 have been preserved, and in 

 most cases a sample thirty years old exists, so that a com- 

 parison of the carbonate of lime in these old samples with those 

 taken recently affords a means of determining the losses to 

 which this substance has been subject. Certain technical diffi- 

 culties concerned with soil sampling and the inevitable irregu- 



