578 ANNUAL REPORT OF THE Off. Doc. 



RESULTS OF THE MAINE STATION EXPERIMENTS. 



lii every case ilie acid rock gave the best returns. The gaiu was 

 especially marked with the family Gramineae, three members of 

 which, the barley, corn and oats, yielded nearly double the amount 

 produced by either the floats or Eedonda. The effect upon the sun- 

 flowers and buckwheat was especially marked, but if these plants 

 could have been brought to full development it is probable the gain 

 would have been less apparent. 



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

 rouk 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. lu 

 other words, the effect of the available phosphoric acid, as com- 

 pared with the insoluble phosphate, was to increase the product 

 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 Cruciferae 

 gave returns within ten per cent, of those obtained by the acid 

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

 ever, for there the good effects of the acid rock were more marked. 



Of the three forms of phosphate used, the Kedonda proved the least 

 valuable, though supplying a larger amount of available phosphoric 

 acid than the floats. In most cases, it showed itself inferior even 

 to floats. The Germineae furnished an interesting exception to 

 this rule, yielding results with Eedonda above those given by the 

 floats. 



The small yield from the boxes in which no phosphate was used 

 is sufficient indication of the extreme poverty of the soil, and con- 

 firms the belief that the amount of phosphoric acid thus supplied 

 is not sufficiently large to seriously affect the experiment. 



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

 a remarkable agreement in their behavior towards the various phos- 

 phates. The striking manner in which the Gramineae respond 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 conduct toward the Ke- 

 donda. The relative value of this phosphate and floats is here the 

 reverse of that shown by nearly all the other plants. The failure 

 of the Cruciferae to respond to the acid rock furnishes a good illus- 

 tration of a similar kind. The Umbelliferae. though responding to 

 the acid rock, seem to derive no benefit from either the floats or 

 Rendonda. since neither of the phosphates increase the yield above 

 that obtained where no phosphates were used. This is true both 

 of the whole plant and the roots. 



