REVIEW OF PREVIOUS EXPERIMENTS 17 



Commenting on these figures the writer of the Bulletin says : 



Taking the average results of the three years, the crop from this plot (3) 

 has been about one ton per acre less than that from the basic slag and super- 

 phosphate plots. Under normal conditions it is the cheapest form of phos- 

 phatic manure, and, provided that it is finely ground, it may be recommended 

 for use in the wet climate of North Wales. It is, however, more likely to prove 

 of general value for poor pastures on peat or upland soils, than for swedes on 

 ordinary cultivated soils. Even an extra crop of one ton per acre of roots 

 would more than cover the difference between the cost of suitable dressings 

 of slag and mineral phosphates. 



The above experiments with rock phosphates are by no means 

 exhaustive, nor does this summary take account of all the countries 

 where experimental work with such phosphates has been conducted. 

 The Commonwealth Government of Australia, for example, has 

 offered a prize for the discovery of new phosphate deposits, and an 

 account of some preliminary experiments with these materials in 

 Western Australia is given by PatersonUT). 



The field experiments which have been conducted in this country 

 are not convincing, as they have failed to establish the value of rock 

 phosphates in the same sense that the Cockle Park and similar experi- 

 ments established the fertilising value of basic slag. Moreover, no 

 explanation has been forthcoming which satisfactorily accounts for 

 the favourable results secured at Wiston in Sussex and in Aberdeen- 

 shire when compared with slag, and the unfavourable results at 

 Saxmundham when compared with the same material. 



It is obvious that data from many more field experiments is neces- 

 sary, and if the trials are to be really helpful, each experiment must 

 cover a series of years, and an endeavour be made to correlate the 

 results with climatic and soil conditions. 



R.B.S. 



