REVIEW OF PREVIOUS EXPERIMENT'S 15 



of lime, but in this instance also it was not so effective as ' Spanish 

 phosphorite and sulphuric acid.' 



Dr Jamieson 1 reports two experiments, one conducted in Sussex 

 and the other in Aberdeenshire, to test if basic slag really acted as 

 effectively as coprolites, both being used in the same state of division 

 and in such quantities as gave equal proportions of phosphate. 



The results were as follows : 



WISTON GLASTBBBEEBY 



(in Sussex) (in Aberdeenshire) 



tons cwts. tons cwta. 



No phosphate ... 25 17 6 16 



Coprolite 28 11 29 1 



Slag 28 11 28 11 



Superphosphate ... 30 7 24 19 



Commenting on these results, Jamieson says: 



The Sussex soil turned out to be too rich to show distinctly the effect of 

 any kind of phosphate, but the Aberdeenshire soil gave conclusive proof. The 

 resulting crops of turnips showed that slag and coprolites, in equal state of 

 division, are practically identical in their effects on crops. 



Gilchrist records (12) a series of four field trials on three years' ley 

 to compare the value of Belgian and Tunisian phosphates with basic 

 slags of varying solubilities. Two of the series give results very favour- 

 able to Tunisian and Belgian phosphates. The third test, however, 

 is not so favourable, and the fourth test had to be abandoned owing 

 to the failure of the 'clover take.' In the first of Gilchrist's three 

 year tests Tunisian phosphate does not do so well as Belgian, a result 

 which Gilchrist attributes to this phosphate not being so rich in lime. 

 It is worthy of note that in the second test Gilchrist gets somewhat 

 better results from Belgian phosphate that has been calcined. 



Oldershaw(i6), working on a chalky boulder clay soil in Suffolk, 

 found that on the hay crop, citric solubility was of great importance. 

 Although low citric soluble slags and a Belgian rock phosphate effected 

 a considerable improvement, the high soluble slag gave a much heavier 

 hay crop than the rock phosphate or the low soluble slags. In dis- 

 cussing his results, Oldershaw makes the following observation, which 

 is of considerable importance: "It is worthy of note that had all the 

 plots been grazed and the results estimated by inspection only, the 

 conclusion might easily have been drawn that Plots B (low soluble 

 slag) were almost as good as Plots A (high soluble slag)." 



1 The Farmer's Handbook, p. 46. 



