ROTATION OF CROPS. 227 



ish turnips, it is seen that by far the greater part of the nitro- 

 gen of the crops was accumulated in the edible root. 



The Nitrogen in the Barley Crops. — The second division of 

 Table 61 shows the average amounts of nitrogen per acre per 

 annum over the eight years in the rotation and in the contin- 

 uous barley crops respectively. 



Beferring to the results chiefly in their bearing on the 

 question of the position of the barley crop in rotation, and of 

 its dependence, or otherwise, on the soil for its supplies of 

 nitrogen, the amounts of it in the total crops, grain and straw 

 together, are of most interest. 



When considering similar results relating to the first crop No man- 

 of the course — the Swedish turnips — it was seen that the ure - 

 average amount of nitrogen per acre per annum in the total 

 crops, roots, and leaves together was only 10 or 11 lb., or 

 even less, when grown without any manure. The results 

 relating to the rotation barley crops show, however, that the 

 average annual removal in them was without manure nearly 

 30 lb.; the conditions of growth being substantially equiva- 

 lent to fallow, as practically no root-crop had been removed. 



Consistently with other evidence on the point, the amounts With 

 of nitrogen removed in the barley crops grown on the super- su ^ pfws ' 

 phosphate plots are seen to be even considerably less than 

 without manure, where the increased crop of roots grown 

 under the influence of the superphosphate had been removed 

 from the land ; but where the superphosphate turnips had 

 been fed on the land, the amounts of nitrogen removed in the 

 barley crops are more than under the parallel conditions with- 

 out manure. In other words, an increased amount of nitrogen 

 having been taken up from the soil by the turnips under the 

 influence of the superphosphate, the land was left poorer in 

 available nitrogen for the barley where the increased turnip 

 crop had been removed from the land, but richer where it, 

 or its manurial residue, was left upon it. 



Again, under the influence of the mixed manure, supplying Mixed 

 a liberal amount of nitrogen for the roots, which took up a nMnure ' 

 considerable quantity of it, there was much less nitrogen in 

 the succeeding barley, where the roots so grown had been 

 removed, than where they or their manurial residue had been 

 left on the land. 



The actual quantities of nitrogen removed in the barley 

 crops, where the roots had previously been removed, were — 

 without manure nearly 30 lb., with superphosphate about 23| 

 lb., and with the mixed manure about 40 lb.; but where the 

 roots had been fed or left on the land, they were, without 

 manure about 28 lb., with superphosphate more than 30 lb., 

 and with the mixed manure containing nitrogen about 47 lb. 



