104 



LIME REQUIREMENT OF THE SOIL 



Figs. 27 and 28, it will be seen that each successive application of 

 basic slag results in a big increase in live weight gain during the two 

 seasons following its application. Thereafter the live weight increases 

 rapidly decline until a fresh dressing is applied, clearly indicating 

 that during the third, fourth, fifth and sixth seasons following the 

 application of the heavier dressings of basic slag bigger returns could 

 be obtained by a further dressing of phosphates. Gilchrist(i4) and 

 Somerville(29) have pointed out that far from there being a falling 

 off in the response to basic slag at Cockle Park, the live weight gains 

 are gradually increasing over each six year period. The improvement 

 is slow, but it is due to the very slow building up of the phosphoric 



160 



11-0 



120 



100 



80 



60 



40 



20 



Year 



FIG. 28. Live Weight Gains on Basic Slag and Untreated Plots at Cockle Park. 

 Second Period, 1906-1911. Untreated Plot Basic Slag Plot . 



acid content of the soil. Such a result serves to confirm the conclusion 

 that phosphoric acid is still the limiting factor at Cockle Park, and 

 that until the demand for phosphates is satisfied it will not be possible 

 to establish a permanent plant of clover and no improvement in the 

 condition of the clover plant or in the live weight gains can be antici- 

 pated by either the addition of lime or of potash. 



WHY THE CLOVER FAILS ON SOME PASTURES IN ESSEX 

 DURING THE DRY SEASON 



If the failure to secure a permanent bottom of clover on Tree Field 

 at Cockle Park is due to an inadequate supply of phosphates in the 

 soil, such is not the case at the experimental centres in Essex where 

 this difficulty has been experienced. 



An inspection of Fig. 26 shows quite convincingly that at Martin's 

 Hearne and Tysea Hill phosphoric acid is no longer a limiting factor 



