THE ESSEX EXPERIMENTS 29 



In spite of the fact that the amount of available phosphoric acid 

 in this soil is very low, the response to the various phosphates, judged 

 by the yield of hay, is insignificant. The improvement in the three 

 treated plots was, however, obvious on walking over them. The clover 

 bottom on the untreated plot was very patchy and a considerable 

 area of the plot was bare. Plots 1, 2 and 4 were covered with a thick 

 bottom of wild white and red clover. In the earlier years of the 

 experiment Plot 2 had undoubtedly the better bottom, but was 

 closely followed by Plot 4, which in 1920 was probably slightly the 

 better plot. Plot 1 open hearth fluorspar slag was inferior to 

 Plot 2 during the first three years of the experiment, but during 

 1920 this plot made considerable progress and was quite comparable 

 with the other two treated plots. 



During August, 1919, a determination of the ground space occupied 

 by the various species on each of the four plots was made and the 

 results set out in Table XIII and illustrated in Fig. 3. The high citric 

 soluble slag has produced a vast improvement in the herbage, and 

 it is quite clear from these comparative results that up till then it 

 had been the most effective phosphate. 



Although the meadow is an early one, being generally cut during 

 the last week in June or the first week in July, still it is somewhat 

 surprising that the effect of the phosphate should be confined to 

 stimulating the bottom growth and that the improvement so brought 

 about should have practically no effect on the yield. The results 

 seemed to indicate that until some other requirement of the soil is 

 satisfied the yield of hay will not be greatly affected by the applica- 

 tion of phosphate. 



DISCUSSION OP THE RESULTS ON THE BOULDER CLAY SOILS 



At Tysea Hill and Martin's Hearne the two types of soluble slag, 

 namely, the basic Bessemer and open hearth basic slag without 

 fluorspar, produce in equivalent quantities the same results. The 

 open hearth fluorspar basic slag of 45 % citric solubility gives returns 

 strictly comparable with the other two types of slag. The fluorspar 

 slag of very low solubility (20 %) does not do so well and it is distinctly 

 inferior at Martin's Hearne (Table X) and Farnham (Table XIII) 

 to the more soluble types of slag. The soils at the two centres 

 Martin's Hearne and Tysea Hill are practically identical, and it 

 would be reasonable to expect that the fluorspar slag of 45 % solu- 



