22 THE ESSEX EXPERIMENTS 



experimental centres, namely Horndon and Hassobury, plots dressed 

 with superphosphate, superphosphate and lime, and lime alone, have 

 been included. With one or two exceptions the phosphates were sown 

 during the period December to the end of February. Unless speci- 

 fically mentioned the initial dressing given was equivalent to 200 Ibs. 

 of P 2 O 5 per acre, and no further dressings have since been applied. 

 The hay crop was cut during the latter part of June and July, and the 

 whole of the crop on each plot weighed immediately before stacking. 

 In order to secure uniformity and accuracy the manures were sown, 

 the hay crop cut, and weighed under the personal supervision of the 

 writer. The necessary labour for weighing the crop on the experi- 

 mental plots was brought direct from Chelmsford, and by such means 

 interference in the usual routine of the farm during what is a busy 

 season was minimised, and it was possible to keep the experiments 

 under very effective control. 



FIELD EXPERIMENTS ON BOULDER CLAY SOILS 



Tysea Hill Farm. As far as can be ascertained this field has 

 always been under grass, and for at least thirty years prior to the 

 laying down of the plots in 1915 had been hayed and grazed in 

 alternate years. It is known that prior to 1915 this field had received 

 no treatment with artificial manures whatever, although it may, 

 many years ago, have received occasional dressings of farmyard 

 manure. The soil is sour judged either by the lime requirement figure 

 or the Ph. value. The results are given in Table IX and are sum- 

 marised in Fig. 1. 



At Tysea Hill there was a rapid and marked response to the various 

 phosphates. During the first season the Gafsa rock phosphate plot 

 was backward, but during the succeeding years was quite as good 

 as any of the other plots on the field, and over the period of the 

 experiments the rock phosphate has proved quite as effective as the 

 best quality basic Bessemer slag. 



In the first year of the experiment there was an improvement in 

 the quantity of clover present in the herbage on the treated plots, 

 but at no period of the experiment was clover present to a very 

 marked extent. Although during the last three seasons the untreated 

 plots could be distinguished from the treated by the much smaller 

 bulk of growth on them, there was never any striking difference 

 between the amount of clover present on the untreated and treated 

 plots. During the winter the untreated plots could always be dis- 



