AN INVESTIGATION INTO THE REASON 



WHY BASIC PHOSPHATES HAVE CAUSED 



INCREASED YIELDS 



THE EFFECT OF PHOSPHATES ON THE BOTANICAL 

 COMPOSITION OF THE HERBAGE 



MIDDLBTON ( 1 5) in his paper on ' ' The Improvement of Poor Pastures " 

 puts to himself the following question: "Why do phosphates produce 

 so rapid an increase?" He states that a study of tables recording 

 live weight gains or yields of hay will not supply the answer, but 

 "that the pastures themselves when closely examined clearly explain 

 the action of the manures." He attributes the results to: (1) the 

 very rapid increase in the leguminous herbage which takes place; 



(2) a rapid improvement in the quality of the surface soil; and 



(3) the accumulation of atmospheric nitrogen fixed by the nodule 

 organisms. He gives it as his opinion, formed from his careful inspec- 

 tion of the various experiments, that phosphates have little or no 

 direct action on the grasses, and that it is the lime in the basic slag 

 acting on the nitrogen accumulated by the nodule organisms which 

 brings about the improvement in the grasses. This improvement 

 does not take place until the clover has been well established. Finally 

 Middleton concludes that it is impossible to obtain a purely legu- 

 minous herbage, that clovers will partly and sometimes almost com- 

 pletely disappear in three or four years as a consequence of the 

 competition of the grasses encouraged by the nitrogen accumulated 

 in the soil by the clover nodule organisms. Gilchrist comes to very 

 much the same conclusions in his reports on the Tree Field results. 



In order to obtain more detailed information concerning the effect 

 of phosphates on the composition of the hay crops in Essex, botanical 

 analyses of the hay on the plots at several centres were made during 

 the season of 1919, the samples being taken the same day as the hay 

 was cut. 



Martin's Hearne and Tysea Hill. The results from the experi- 

 mental centres at Martin's Hearne and Tysea Hill are set out in 

 Tables XXII and XXIII. 



R.B.S. 



