60 



EFFECT OF PHOSPHATES 



organic matter content of the soil are already high, and it is difficult 

 to believe that the accumulation of a comparatively small amount 

 of nitrogen by the nodule organisms and its subsequent nitrification 

 is responsible for the double crop which the treated plots bore in 

 1919 when no clover was present. It seems more probable that the 

 double crop is due either to the grasses benefiting by the direct 

 fertilising effect of the phosphates or to the phosphates having some 

 action on the production of nitrates in the soil, or to the operation of 

 both these causes. This contention is borne out by the results at 



TABLE XXXII. BOTANICAL COMPOSITION OF THE HAY BY WEIGHT 



ON THE PLOTS RECEIVING HlGH SOLUBLE BASIC SLAG. SEASON, 1919 



* The figures for Farnham and Horndon indicate the percentage of ground space 

 covered by the various species and not the botanical composition of the hay. It is 

 obvious however that had a hay crop been cut at these centres clover would have 

 formed a large proportion of the crop by weight. 



t May 1st till Harvest. 



Lambourne End, where a very large increased crop of grasses follows 

 the application of phosphates, the response of the clovers to the 

 dressing not being manifest until the following year (see Tables XXVII 

 and XXVIII). 



Table XV clearly shows the superior effect of basic phosphates in 

 encouraging the growth of clovers, but this effect once produced is 

 not maintained on all the soils until the dressing of basic phosphates 

 is exhausted or nearly so. 



At Horndon, Latchingdon, Saffron Walden and Farnham no diffi- 

 culty has been experienced in maintaining the clover even during a 

 dry and unfavourable season like 1919. At Martin's Hearne, Tysea 

 Hill and Lambourne End, however, the clover completely disappeared 

 from the treated plots during 1919. This result at Martin's Hearne was 

 rather surprising in view of the fact that clover covered the treated 

 plots in 1918 almost to the exclusion of the grasses (see Plate IV). 



