No. 4.] CHEMICAL AND FARM MANURES. 139 



was made, annually, with the expectation that it would 

 probably be sufficient to supply the needs of the plants. It 

 is possible, however, that the nitrogen of the bone never- 

 theless exerted some effect ; but, even if this were the case, 

 the gain of the bone over the floats was small, amounting 

 to only 372 pounds of hay per acre, annually, in the highest 

 instance. The total net gain from the use of the floats, 

 determined by deducting the yield upon the plots receiving 

 no phosphates, amounted, in the case of the unlimed plot, 

 to 8,012 pounds of hay, and in the case of the limed one, 

 to 4,787 pounds. From this the effectiveness of the floats 

 is strongly evident. The after-effect of the one ton of lime 

 per acre in connection with the floats resulted in nearly 

 doubling the yield of hay, while upon the plots receiving 

 no phosphoric acid for the entire period the lime increased 

 the crop of hay from 2,548 to 15,738 pounds. That the 

 gain from the use of floats was so much less where the lime 

 was employed was due, probably, to the absence of carbon- 

 ate of lime in the soil, whereby the lime of the floats was 

 directly helpful to the plants ; and, furthermore, in the 

 absence of the lime the solvent action of the soil upon the 

 phosphate was materially increased. Another factor, how- 

 ever, probably exerted more influence than both of these 

 combined, namely, the setting free by the lime of a large 

 amount of phosphoric acid from the soil itself, which would 

 of course reduce the apparent effect of that supplied artifi- 

 cially. In support of this, it may be cited that in a soil 

 test by means of chemicals and Indian corn, conducted at 

 the Rhode Island station, a most marked deficiency of 

 phosphoric acid seemed to exist, potassic and nitrogenous 

 manures proving of but limited value for several years. 

 The plots were then limed at the rate of two and one-half 

 tons to the acre, with the result that where only nitroge- 

 nous and potassic manures were applied the crops have 

 since been excellent, due apparently to the liberation of 

 phosphoric acid from the soil, notwithstanding the fact that 

 but little if any phosphoric acid had been applied to the 

 land for from fifteen to twenty years. 



SuflScient has been said above to show the cumulative 

 efiect of applications of bone and of floats ; but attention 



