16 REVIEW OF PREVIOUS EXPERIMENTS 



Scottish Experiments. In Bulletin 10 of the North of Scotland 

 College of Agriculture details are given of an experiment extending 

 over three years, and designed to contrast the effect of superphosphate, 

 bone meal, basic slag, and ground Florida phosphate, with and with- 

 out farmyard manure, on turnips and the two succeeding crops, barley 

 and hay. In the series of plots comparing the four phosphates without 

 the addition of farmyard manure, the American rock phosphate gives 

 the poorest result. It has approximately the same effect on the barley 

 and hay crops as basic slag, but did not prove to be as effective on 

 turnips. 



On the other hand, where farmyard manure was given in addition 

 to the various phosphates, Florida rock phosphate gave better results 

 than any of the other phosphates, and the profit on the rock phos- 

 phate plot is more than twice as great as on any of the others. It is 

 difficult to draw conclusions concerning the relative efficiency of these 

 phosphates when used with farmyard manure. No plot with farmyard 

 manure alone was included in the series, and it might well have 

 happened that farmyard manure alone would have given as good 

 results as farmyard manure plus phosphate. 



Russell(24), in "Notes on Manures" for Jan. 1920, gives a table 

 summarising 67 experiments on the turnip crop in Scotland during 

 1911-14 with various types of phosphates, including ground mineral 

 phosphates. The results show that such phosphates are very nearly 

 equivalent to basic slag. It is not clear from this summary, however, 

 how much of the gain, amounting to 6 or 7 tons, of the treated plots 

 over the untreated is due to the application of phosphoric acid, as 

 the treated plots received in addition to the various types of phos- 

 phates a dressing of sulphate of ammonia and potash salts. 



Welsh Experiments. Trials with basic slag, Gafsa rock phosphate, 

 and superphosphate on Swedes were carried out by the University 

 College of North Wales during the three seasons 1913-1915 1 . Each 

 of the phosphates was applied so as to supply 200 Ibs. of phosphoric 

 acid per acre. The response to phosphoric acid is decided, and the 

 results which are given below are of considerable value. 



AVEBAGE YIELD 



Plot 1 

 2 

 3 

 4 



