THE ESSEX EXPERIMENTS 43 



The open hearth fluorspar slag of 45 % solubility on the average 

 of five years seems to be quite as effective at Latchingdon as the 

 most soluble types of slag, although it seems to be somewhat less 

 effective during the fourth and fifth years of the experiment. 



The low soluble open hearth fluorspar slag (20% soluble), although 

 it gave promise of good results at Horndon during the first two 

 seasons, fell far behind during the favourable season of 1920, and 

 proved to be inferior to the more insoluble types of rock phosphate. 

 This slag also proved less effective on the boulder clay soil at Martin's 

 Hearne (Table X). It is not suggested that this slag is of little value. 

 On the contrary the improvement effected is really very marked in 

 all cases, and only suffers by comparison with the other phosphates. 



FIELD EXPERIMENTS ON CHALK SOILS 



Wendens, Saffron Walden. The lower photograph on Plate VII 

 illustrates the character of the soil at this centre. The chalk is covered 

 by a thin layer of boulder clay soil, mixed with a large proportion 

 of chalk. The first nine inches of soil at Wendens contains upwards 

 of 36 % of chalk. It is naturally comparatively rich in phosphates, 

 and although the available phosphoric acid figure is low (Table VII) 

 this is no doubt due to the calcium carbonate neutralising the citric 

 acid. This type of soil dries out quickly. It therefore makes an early 

 start in the spring, and the meadow hay is always ready to cut during 

 the second or third week of June. In this respect, therefore, the 

 conditions are somewhat different from those at the other experi- 

 mental centres, which are known as late meadows and which are 

 not harvested before the second week of July. 



The experimental field at Wendens was allowed to fall out of 

 cultivation about 25 years ago. No seeds of any description were 

 sown, and the meadow is therefore a natural one. The general practice 

 has been to cut the field every year for hay, and to fold the aftermath 

 with sheep. The pasture is of a much superior type to that on any 

 of the other experimental centres. The same phosphates were used 

 at this centre as at Latchingdon and Tysea Hill Farm. The weights 

 of hay for the five years 1916-1920 are given in Table XIX, and 

 are represented diagrammatically in Fig. 6. 



The results at this centre are of considerable interest because they 

 show that even on an early meadow the more insoluble types of 

 phosphate, such as those represented by rock phosphates and the 

 better types of open hearth (fluorspar) basic slag, are capable of 



