236 



THE ROTHAMSTED EXPERIMENTS. 



Rotation 

 and contin- 

 uous crops. 



Clover. 



Beans. 



Effects of 

 manures. 



Rotation 

 and contin- 

 uous crops. 



mixed manure, containing, besides superphosphate, salts of 

 potash, soda, and magnesia, and nitrogen also. But, under 

 all three conditions as to manuring, the continuously grown 

 crops take up much less than those grown in rotation. 

 Whether, however, grown in rotation or continuously, three, 

 four, or more times as much of the phosphoric acid is finally 

 accumulated in the corn as remains in the straw. In refer- 

 ence to all the results with beans, however, it is to be borne 

 in mind that under none of the conditions were good crops 

 obtained. 



The clover took up, without manure, little more phosphoric 

 acid than the rotation beans ; but, with superphosphate, the 

 clover took up more than twice as much as the beans ; and 

 with the mixed manure it took up more still, and also more 

 than twice as much as the beans grown under the same 

 conditions. 



Taking the average of the six crops of beans and two crops 

 of clover grown in the eight courses, there was, both without 

 manure and with superphosphate, much less phosphoric acid 

 taken up than in either the preceding barley or the succeed- 

 ing wheat ; and even with the mixed manure, which gave the 

 most normal crops, the average amount of phosphoric acid 

 taken up in the beans and clover was less than in either of 

 the two cereals under the same conditions. 



The Phosphoric Acid in the Wheat Crops. — The bottom di- 

 vision of Table 63 shows that the rotation wheat, as did the 

 rotation barley, took up very much more phosphoric acid 

 without manure than did either of the so-called fallow crops 

 — the turnips or the leguminous crops. With superphosphate, 

 again, both the wheat and barley took up more than either 

 the turnips or the average of the leguminous crops. With the 

 full mixed manure, however, when each of the four descrip- 

 tions of crop grew more normally, the amount of phosphoric 

 acid taken up was more nearly uniform in the four cases ; 

 the barley, however, then yielding more than the wheat, more 

 than the turnips, more than the average of the leguminous 

 crops, but all considerably less than the average of the two 

 years of clover. 



Comparing the amounts of phosphoric acid in the total 

 produce of the rotation with those in the continuously grown 

 wheat, it is seen that there is, without manure, only about 

 half as much taken up in the continuous as in the rotation 

 crops ; with superphosphate, again, only about half as much 

 in the continuous as in the rotation ; but with the more nor- 

 mal growth, when the full mixed manure was annually applied 

 to the continuously grown crops, there was, with the fuller 

 produce, proportionally much more phosphoric acid taken up 



