24 THE ROTHAMSTED EXPERIMENTS. 



given the amounts per acre of each of these constituents, in 

 the roots and leaves respectively, and the amounts per acre, 

 more or less, in the leaf than in the root. 

 Effect of Thus, with the Norfolk white turnip we have less than one- 



Imf^nd 11 tn ^ r( ^ as mucn l e& f as r0 °t without nitrogenous manure, but 

 root. nearly two-thirds as much with the largest supply of nitrogen 



by manure — that is, with the greatest luxuriance of growth. 

 The economic importance of the difference in the propor- 

 tion of leaf to root, under the influence of different conditions 

 as to manuring, is illustrated by the other results given in 

 the table ; and similar results given in corresponding tables 

 relating to Swedish turnips, sugar-beet, and mangel-wurzel, 

 will show how great is the difference in this respect between 

 different descriptions of root-crops. 



In the case of the Norfolk white turnips, not only is there 

 a large proportion of leaf, but the leaf contains a very much 

 higher percentage of dry matter than the root, and there is 

 a very much higher percentage of both nitrogen and total 

 mineral matter in the dry substance of the leaf than in that 

 of the root. 



The significance of these facts is more clearly brought out 

 in the lower division of the table, which shows the amounts 

 per acre, in root and in leaf respectively, of dry matter, of 

 nitrogen, and of total mineral matter, under the different 

 conditions of manuring ; also the amounts of these in the 

 leaf + or — the amounts in the roots. 



It is seen that there was in one case, that with the highest 

 nitrogenous manuring, nearly as much dry or solid matter 

 per acre in the leaf, which for the most part only becomes 

 manure again, as in the edible part of the crop — the root. In 

 three cases there is actually more of the nitrogen of the crop 

 in the leaf, remaining for manure, than there is in the portion 

 available as food. There is also, in two cases, more of total 

 mineral constituents in the leaf than in the root. 



2. Experiments with Swedish Turnips. 



Swedes. The experiments with the Swedish turnip — Brassica cam- 



pestris rutabaga — were made in the same field, on the same 

 plots, and with to a great extent similar manures, as in the 

 case of the Norfolk white turnips already considered. The 

 mineral manures were in fact practically the same through- 

 out, and the nitrogenous manures were nearly the same in 

 the first two of the four years, 1849 and 1850, but in the 

 second two no nitrogenous manures were used. Further, 

 the results were obtained in the next succeeding four years 

 to those in which the Norfolk whites were grown. 



