THE ESSEX EXPERIMENTS 41 



had the high lime requirement of -45 %, and was highly charged 

 with organic matter. 



The results are given in Table XVIII. 



Although there are considerable differences between the effect of 

 the various phosphates at this centre during the dry season of 1919, 

 there are no decided indications that high citric solubility has been 

 of any great importance. The noticeable difference between the returns 

 from the two types of open hearth fluorspar basic slag (Plots 1 and 7) 

 is somewhat surprising, especially as it is the more soluble of the 

 two slags which gives the poorer result. It has, however, been pointed 

 out (18) that a modification of the solubility test, so that 1 gin. instead 

 of 5 gms. of the phosphate is used in performing the test, reverses the 

 order of solubility of these two slags. The slag on Plot 1 becomes 

 60-6 % soluble whilst that on Plot 7 is only 37-7 % soluble. Difference 

 in the nature of the phosphates in the two slags is evidently in this 

 case of greater importance than any question of solubility by the 

 Wagner citric acid test. 



During the dry season of 1919 clover was practically absent from 

 these plots, and it was not until May of 1920 that it began to force 

 its way through the matted turf on the treated plots. In June the 

 progress made was remarkable, and by the end of the month the 

 treated plots were covered with a thick and vigorous growth of red 

 and white clover, which over large areas practically precluded the 

 growth of any other type of vegetation (Table XXVIII). The clover 

 on Plot 2 (high soluble slag) made better progress than that on Plot 1 

 (low soluble slag), and on the whole the high soluble slag was the 

 better of the two. The difference was noticeable at the beginning 

 of the season, but towards the end it became less and less visible. 

 Throughout the whole season Plot 7 (open hearth fluorspar basic 

 slag) was much inferior to any of the other plots, and it was rather 

 surprising to find it weigh out so heavily. The Cleveland phosphate 

 plot was perhaps the best plot on the field, although the superiority 

 was not great. The Florida pebble phosphate was slow in making a 

 start, but this plot made rapid progress and was ultimately one of 

 the best plots on the field. 



In spite of the dry season the 1921 hay crop was quite a heavy 

 one, whereas at Martin's Hearne, only a short distance away, the crop 

 was practically a failure (Table X). The contrast is probably due to 

 the difference in the soils. The heavy soil at Martin's Hearne 'bakes 

 and cracks' during a hot and dry spell of weather, and under such 

 circumstances it is likely that the greater part of the heavy fall of 



