72 MAINE AGRICULTURAL EXPERIMENT STATION. 



RESULTS. 



In every case the acid rock gave the best returns. The gain 

 was especially marked with the family Gramines. three mem- 

 bers of which, the barley, corn and oats, yielded nearly double the 

 amount produced by either the floats or Redonda. The effect 

 upon the sunflowers and buckwheat was equally marked : but if 

 these plants could have been brought to full development it is 

 probable that the gain would have been less apparent. 



If we compare the amount of dry matter produced by the acid 

 rock with that produced by the floats for all the crops grown, 

 we find the balance in favor of the acid rock to be 52 per cent. 

 In other words, the eltect of the available phosphoric acid as 

 compared with the insoluble phosphate was to increase the prod- 

 uct more than one-half. 



In nearly every case the floats gave results second only to those 

 obtained with the acid rock. With this phosphate the Cruci- 

 ferse gave returns within ten per cent of those obtained by the 

 acid rock. This is not true of the edible portion of these plants, 

 however, for there the good effects of the acid rock were more 

 marked. 



Of the three forms of phosphate used, the Redonda proved the 

 least valuable, though supplying a larger amount of available 

 phosphoric acid than the acid rock. In most cases it showed 

 itself inferior even to the floats. The Graminese furnished an 

 interesting exception to this rule, yielding results with Redonda 

 above those given b\' the floats. 



The small yield from the boxes in which no phosphate was 

 used is sufacient indication of the extreme poverty of the soil, 

 and confirms the belief that the amount of phosphoric acid thus 

 supplied is not sufficiently large to seriously aftect the experi- 

 ment. 



It is interesting to note that plants of the same family show 

 a remarkable agreement in their behavior towards the various 

 phosphates. The striking manner in which the Graminese 

 responded to the stimulus of the acid rock has already been 

 alluded to. In no other case is the effect so marked. Another 

 peculiarity of the members of this family is shown in their con- 

 duct toward the Redonda. The relative value of this phosphate 

 and floats is here the reverse of that shown bv nearlv all the 



