26 



not sensibly affect the succeeding barley crops on these plots, 

 while the removal of the roots was always felt on the super- 

 phosphate plots. On the other hand, we have to remark that 

 the great apparent loss of barley on the superphosphate plots 

 is confined to the three years when the roots not carted 

 were fed off on the land by sheep ; in the five years in which 

 the turnips were sliced and ploughed in, the carting of 9 tons 

 4f cwts. of roots occasioned an average loss of 5f bushels of 

 barley, a rate not very different from that shown on the highly 

 manured division. It seems possible that the sheep feeding 

 off the turnips grown by superphosphate alone, without any 

 cake or corn in addition, and with a minimum of straw 

 chaff, were in a condition of nitrogen starvation, and that 

 more nitrogen passed in their urine to the soil than was 

 supplied by their food. 1 It was known, indeed, as a fact, 

 that the sheep rapidly fell off in condition. In consequence 

 of this manuring of the land by the sheep, the plots where 

 the turnips were fed off would yield more barley than they 

 should have done, and the injurious effect of carting the 

 turnips on the other plots was thus exaggerated. Looking at 

 the whole of the results, we shall perhaps be near the truth if 

 we assume that the carting of 10 tons of swedes with their 

 leaves may be expected usually to diminish the following barley 

 crop by about 6 bushels. 



What has been the effect of carting the turnip crop upon 

 the other crops of the rotation? To answer this question 

 we will take the mean of ten rotations, including all except 

 the first, and the one in which the turnip crop entirely failed. 

 Looking first at the richer land, where the swedes received an 

 abundance of nitrogenous manure, we find that the entire 

 removal of the roots, averaging 16 tons 15| cwts. in each 

 rotation, produced practically no effect upon the other crops 

 in the rotation, with the exception of the barley already 

 noticed. The exhaustion produced by carting is not shown in 

 the turnip crop, for this is on an average half a ton better on 

 the plots where the turnips had been carted. It is perceived 



1 If the swedes contained -4 per cent, of true albuminoids (-394 per cent. 

 was found by analysis in the superphosphate swedes of 1880), the sheep 

 would daily have to consume turnips equal to one-quarter of their live weight 

 to preserve a condition of nitrogen equilibrium. 



