ROTATION OF CROPS. 235 



acre, with superphosphate about 18 lb., and with the mixed 

 manure nearly 25 lb. In the case of the phosphoric acid, 

 therefore, as in that of the nitrogen, the influence of the manu- 

 ring, and other treatment, of the preceding crop of the course, 

 is clearly reflected in the amounts taken up in the succeeding 

 barley. 



Comparing the amounts of phosphoric acid in the rotation Rotation 



barley crops with those in the continuously grown ones, it is and conhn - 

 "i \ i . i • i i ii uous crops. 



seen that, both without manure and with superphosphate, the 



rotation crops took up considerably the most phosphoric acid ; 

 and this was the case notwithstanding that the continuously 

 grown crops were annually manured with superphosphate, 

 whilst for those grown in rotation the application had only 

 been for the preceding crop — the turnips. The less assimila- 

 tion in the case of the continuous crops was doubtless due to 

 the diminished total growth, which in its turn was due to the 

 greater exhaustion of the available nitrogen of the soil with 

 the annual growth. Consistently with this view, where the 

 mixed manure supplying an abundance of nitrogen was ap- 

 plied, and the crops, both rotation and continuous, were pretty 

 full averages for the particular soil and the seasons of growth, 

 the amounts of phosphoric acid in the rotation crops where 

 the roots had not been removed were almost identical with 

 those in the continuous crops. Where, however, the rotation 

 roots had been removed, carrying off therefore the whole of 

 the nitrogen that had been taken up, the succeeding barley 

 crops were accordingly not full for the seasons of their growth, 

 and the amounts of phosphoric acid in them were less than in 

 the continuously grown crops. 



The figures relating to both the rotation and the continuous Phosphoric 

 barley further show, that about six-sevenths of the total phos- a g c ^ n and 

 phoric acid of the crops is accumulated in the grain which is straw of 

 supposed to be sold off the farm. There was, indeed, even a oarle v- 

 somewhat higher proportion where phosphoric acid was sup- 

 plied in the manure. Lastly, as in the cases of the total pro- 

 duce, the dry matter, and the nitrogen, there is much less 

 difference between the amounts of phosphoric acid taken up 

 under the three different conditions as to manuring than in 

 the case of the turnips. That is, the assumed restorative crop Depend- 

 is much more dependent on direct manuring to yield any e r ^ ts °{ n 

 crop at all than is the cereal crop, which is assumed to be manure. 

 benefited by the interpolation of it. 



TJie Phosphoric Acid in the Leguminous Crops. — Referring to Effects of 

 the third division of Table 63, it is seen that the amounts of manures - 

 phosphoric acid in the total produce of beans (corn and straw 

 together) were more where superphosphate was supplied than 

 without manure, and more still under the influence of the 



