E. J. Russell and A. Appleyard 



•25 



B. The ejfev( of org<niic nmtler. 



Fig. 10 shows the comparison between two plots in Broadbalk wheat 

 field one of which is unmanured while the other receives every September 

 a dressing of 14 tons of farmyard manure. The comparison is only 

 strict during the winter period September to March or April when the 



2-0 



1-5 



|0-8 



30-6 



0-4 



0-2 

 0-0 



Feb. Mar.Apr.Mav Jiinrjiitv Aug.Sept.Oct. Nov. Dec. Jan. Feb..Mar..\pr. May-liino JiilvAuu'.^iopL 



Fig. 10. Comparison of CO2 content of unmanured plot with plot receiving 

 farmyard manure, Broadbalk field. 



crop is 80 small that it can safely be neglected ; from May on to harvest 

 time complication arises from the fact that the dunged plot carries a 

 dense crop while the unmanured plot does not. During winter the air 

 from the dunged plot consistently contains the larger quantity of COg ; 

 we can carry the strict comparison from March onwards by taking the 

 fallow part of the dunged plot and the unmanured fallow on Hoos field, 

 which closely resembles the unmanured plot in Broadbalk : 



Dunged fallow 

 (Broadbalk) 



Unmanured fallow 

 (Hoos) . . 



May 15 



0-22 

 010 



May 25 June 10 , June 12 June 13 July 7 July 27 



0-32 

 0-07 



0-17 

 0-08 



0-36 

 0-07 



0-36 

 0-10 



0-30 

 0-08 



0-35 

 0-09 



The dunged plot still gives the higher result so that the efl'ect of 

 the manure is clearly to increase the amount of COj in the soil air 

 throughout the year. 



