THE ESSEX EXPERIMENTS 33 



the distinction became less and less visible, until at the beginning 

 of July it was quite impossible to see any difference. 



The high soluble basic slag, Plots 5 and 17, and Plot 15 (super 

 and lime) were distinctly ahead during the whole season, but 

 the rock phosphate plots gradually lessened the difference as 

 the season progressed, although they never actually succeeded in 

 catching up. 



The weights of hay for the season of 1920, which was particularly 

 favourable to the hay crop, give some indication of the contrast 

 which existed between the various phosphate plots and the untreated 

 portions. 



It may be of interest to mention that only the plots were cut, and 

 no attempt was made to harvest the rest of the field, as the crop was 

 not considered to be worth the labour involved in doing so. 



When the wild white clover came into flower the contrast was 

 remarkable. Plate VI, showing a general view down Plot K (un- 

 treated) and Plot H (Cleveland phosphate), gives some idea of the 

 contrast which met the eye. So thick was the crop of wild white 

 clover that the farmer decided to seed the plots. 



Plots 1-19 are strictly comparable, having been sown at the same 

 time, and a useful comparison of the effectiveness of the various 

 phosphates may be made from the respective yields of hay. 



There can be little doubt that the highest soluble types of open 

 hearth basic slag and basic superphosphate have proved the most 

 effective phosphates at Horndon. At the same time, however, some 

 of the rock phosphates are nearly as effective. Prom June onwards, 

 for example, it was always difficult to say which of the two, Plots 3 

 or 5, was the better, although there was no doubt that Plot 3 was 

 inferior to Plot 17, which is a duplicate of Plot 5. The hard American 

 Florida pebble phosphate is inferior to the softer North African 

 phosphates. The inferiority is not only apparent in the weights of 

 hay, but is plainly to be seen on walking over the plots, a result 

 which agrees with Tacke's conclusion 1 . 



No gain from fine grinding is apparent in the weights of hay, but 

 an earlier start was undoubtedly made by the plots receiving the 

 finer ground phosphate, and where a meadow is reserved for grazing it 

 is possible that the extra cost of grinding would be well repaid. 



The open hearth fluorspar slag, after giving promising results 

 during the first two years, proved a poor plot in 1920 when compared 

 with the high soluble slag, Plot 17. All the rock phosphate plots, 

 1 Inter. Inst. of Agr. Bulletin, September, 1913. 



R.B.S. 3 



