24 THE ESSEX EXPERIMENTS 



Equally good results it will be noted have been given by the lighter 

 dressing of 100 Ibs. of phosphoric acid over a period of five years, 

 and it would appear that under the soil and climatic conditions of 

 this experiment nothing is to be gained by a heavier dressing than 

 that represented by 100 Ibs. of phosphoric acid per acre. This result 

 is interesting, as the soil is as deficient in available phosphoric acid 

 as that at Cockle Park, where the heavier dressing of 200 Ibs. of 

 phosphoric acid per acre proves much superior to the smaller dressing 

 of 100 Ibs. applied at more frequent intervals (13). 



The effectiveness of the various types of phosphates during the 

 dry seasons of 1918 and 1919 is of considerable interest. The drier 

 the season the greater has been the percentage increase due to 

 phosphates. 



Martin's Hearne Farm. The experimental field at this farm 

 is only half a mile distant from that at Tysea Hill Farm. The soils 

 on the two fields are similar in appearance and in chemical composi- 

 tion. The only noteworthy difference shown by the chemical analysis 

 is the higher potash content of the soil at Martin's Hearne Farm. As 

 far as can be ascertained this meadow has been down to grass for 

 at least eighty years before the experiments began. During this 

 period no artificial manure of any description has been applied, but 

 the meadow has received during the past twenty years at intervals 

 of seven to eight years a dressing of about ten loads of farmyard 

 manure per acre. The herbage is of the poorest quality, weeds such 

 as Rumex acetosa, Centaurea nigra, Stellaria media and Ranunculus 

 forming a very large proportion of the herbage. 



The results of the experiment at Martin's Hearne are shown in 

 Table X and in Fig. 2. The improvement which followed the applica- 

 tion of the various phosphates was even more noticeable than at 

 Tysea Hill. During 1917 a thick mat of wild white and red clover 

 began to cover the various plots, and during 1918 it was so thick 

 on some of the plots as to practically exclude the grasses. The 

 appearance of plots 1, 2, 3 and 4 on June 3rd, 1918 is shown in 

 Plates III and IV. During the first season (1917) the open hearth 

 high soluble basic slag (plot 2) proved more effective than the 

 fluorspar slag or any of the rock phosphates. In 1918, however, the 

 harvest was late, and the season on the whole moister. In this year 

 all the rock phosphates gave results superior to that of the high 

 soluble slag, the superiority of the Gafsa phosphate being quite 

 distinctive. In the dry season of 1919, with an early cutting, the 

 high soluble slag again proved the most effective, whilst in 1920, 



