82 



EFFECT OF PHOSPHATES 



the climatic conditions then prevailing the untreated soil at Martin's 

 Hearne is capable of yielding sufficient phosphate to enable nitrifica- 

 tion to take place at a much more rapid rate than at any other time 

 during the season. 



I 7 



53 * 



33 



1 



JS 29 



March 



IZ 26 



April 



10 24- 

 May 



7 28 



June 



IZ 26 



July 



9 23 



August 



13 Z7 



Sept. 



FIG. 19. Nitrate content of the soil on the Untreated and the Basic Slag Plots at 



Great Mulgraves, Horndon. Soil London clay. Season 1920. 

 Untreated Plot . Basic Slag Plot . Moisture Content 



2-8 

 26 

 24 



a-a 



2-0 

 1-8 

 1-6 

 t-4 

 1-2 



i '..-1 



IS 



March 



S 19 3 17 3i M 28 12 2S S 23 6 2O 

 April May June July August Sept 



FIG. 20. Rainfall at Great Mulgraves, Horndon. Season 1920. 



If, as is postulated here, it is correct, in view of these results, 

 to assume that the main effect of phosphates on the production of 

 nitrate in soils well stored with nitrogenous organic matter is due to 

 their action on the nitrifying organisms, it is possible to explain the 

 large increase in the hay crop obtained on the treated plots at 



