ROTATION OF CROPS. 229 



very much more nitrogen than the beans, and very much Quantity 

 more than either of the other crops of the rotation under £^S 

 parallel conditions. Thus, even without manure, the average by clover. 

 amount of nitrogen in the two crops of clover was — in one 

 case 55 lb. and in the other 47 lb. ; with superphosphate it 

 was 124.5 and 1446 lb.; and with the mixed manure, contain- 

 ing both potash and nitrogen, in the one case 167 lb. and in 

 the other 168.4 lb. Or, taking the average amount of nitro- 

 gen in the six bean and two clover crops, there were — with- 

 out manure 41.5 and 38.9 lb. ; with superphosphate 61.5 and 

 72.9 lb. ; and with the mixed manure 89.5 and 94.7 lb. It 

 is, indeed, to the occasional growth of clover that the very 

 large average amounts of nitrogen removed in the leguminous 

 crops of the rotation are to be attributed; and it is these 

 amounts that have to be taken into consideration in compar- 

 ing the effects on the yield of the other crops of the rotation, 

 and of the rotation as a whole, on the one hand of growing a 

 leguminous crop, and on the other of fallowing, which of 

 course neither yields nor removes nitrogen — unless by loss 

 in drainage. 



Further, the figures show that there was generally three 

 or even more times as much of the total nitrogen of the 

 bean crops accumulated in the corn as remained in the straw. 

 Lastly, not only does the leguminous crop of the rotation 

 yield the most nitrogen, but, unless in the case of some of the 

 corn of the beans, the whole of it is supposed to be retained 

 on the farm ; and there is, in addition, more or less, and some- Nitrogen- 

 times a considerable amount, of nitrogenous crop-residue left f^ombeant 

 within the soil for succeeding crops. 



The Nitrogen in the Wheat Crops. — The results on this 

 head are recorded in the bottom division of Table 61. 



Eeferring first to the amounts of nitrogen in the total pro- 

 duce (grain and straw together), it is seen that, both without 

 manure and with superphosphate alone, that is with the 

 greatest exhaustion, especially of nitrogen, there was gener- 

 ally about, or even more than, twice as much in the rotation 

 as in the continuous crops. With the full manure, both 

 mineral and nitrogenous, applied for the rotation crops only 

 at the beginning of the course, but for the continuous ones 

 each year for the wheat crop to be grown, the relative de- 

 ficiency in the continuous crops was, however, very much 

 less. Thus, the figures show that the average amounts of Effects of 

 nitrogen in the total wheat crops were — without manure di ff erent 

 nearly 3o lb. per acre per annum in the rotation crops, and 

 only 17 lb. in the continuous ones ; with the superphosphate 

 alone nearly 40 lb. under rotation, but in the continuous 

 crops not 20 lb. ; and lastly, with the full manure there was 



