THE ESSEX EXPERIMENTS 87 



applied alone. Superphosphate alone has had most effect on the 

 grasses, whilst superphosphate and lime together basic superphos- 

 phate has told mostly on the clovers. 



Armstrong's method of interpreting the results fails to bring out 

 any marked distinction between the types of basic phosphates. It 

 merely demonstrates that the improvement in quality is approxi- 

 mately the same. When the plots are left for hay the differences 

 between the phosphates are reflected in the hay yields, but when the 

 plots are grazed or when the growth is short inspection of the plots 

 gives the impression that there is little to choose between them. 

 This difficulty in interpreting results under such conditions is also 

 noted by Oldershaw(i6). 



But terfields , Lat chingdon . The soil at Latchingdon is not so heavy 

 as that at Horndon, containing only 16-5 % of clay, against 30 % 

 at the latter centre. The soil would be better described as a clay 

 loam, resting on a stiff London clay subsoil. In other respects it is 

 very similar to Horndon. It is very poor in both total and available 

 phosphoric acid, but contains a small reserve of calcium carbonate. 

 Eight years before the commencement of the experiments in 1915, 

 the experimental field had received a small dressing of about 4-5 cwts. 

 of basic slag per acre a dressing which probably accounts for the 

 comparatively high proportion of citric soluble phosphoric acid to 

 total at this centre (Table VII). 



The meadow, however, was in an exceedingly poor condition when 

 the experiments began, and it is evident from the response to the 

 various phosphates that the effect of the small dressing applied 

 13 years ago was practically exhausted. 



The plots have been cut every year, and the hay crop weighed. 

 The figures are set out in Table XVI and the results are shown 

 diagrammatically in Fig. 5. 



The figures in Table XVI give some idea of the remarkable response 

 to the various phosphates. The improvement in the quality of the 

 herbage was equally marked. During the seasons 1916, 1917 and 

 1918 the treated plots contained a dense and vigorous growth of 

 clover. The open hearth fluorspar slag was quite as effective in this 

 respect, during the initial stages of the experiment, as any of the high 

 soluble slags, and was in fact superior to either of the two open 

 hearth high soluble basic slags on Plots 5 and 6. It has already been 

 pointed out that it was not until the second year that the yellow 

 suckling clover and bird's foot trefoil, which formed the natural 

 leguminous flora of the untreated plot, were replaced on Plot 2 (Gafsa 



