176 



Journal of Agricultural Research 



Vol. XIII, No. 3 



Table IV, — Changes in the limestone requirement from period to period (Series I) 

 [Results expressed as pounds of limestone per 2,ooo,cxx) pounds of soil] 



The strength of the limewater reagent used Vv-as carefully standardized 

 at each period; and even had it not been, the great differences in lime- 

 stone requirement of the manurial mixtures, as compared with the 

 control soil at the successive times of examinations, would bar such 

 reagent variations as an explanation of the facts here recorded. 



It is strikingly shown that the direction in change of limestone require- 

 ment was not continuously the same, but that, while there were some 

 rather marked individual differences, there was, on the whole, a surpris- 

 ing agreement among the substances of the respective groups in the 

 directions, time, and degree of the changes in this property. 



Particularly notable are (i) The great reduction in limestone require- 

 ment during the first two weeks, a decrease on the part of the manurial 

 mixtures to a point far below that of the control soil, in which the 

 requirement underwent no change at this time; (2) a great increase, 

 both absolute and relative, in the control soil in its requirement during 

 the following two weeks; (3) the comparatively slight changes during 

 the second and third months, save in the case of the redtop mixture; 

 (4) a second extensive increase in the requirement during the fourth 

 and fifth months; (5) slight changes during the succeeding months. 



