240 



THE ROTHAMSTED EXPERIMENTS. 



Potash in 

 grain and 

 straw of 

 barley. 



Effects of 

 manures. 



Rotation 

 and contin- 

 uous crops. 



this fact was assumed to be connected with the greater amount 

 of the carbohydrate — sugar — in the roots than in the leaves. 

 The results relating to the barley show, however, that there 

 was in every case more, and in some much more, potash in 

 the straw than in the grain. On this point it is to be 

 observed, not only that the root-crop is taken up when still 

 in the vegetative stage, and its contents are still in the con- 

 dition of reserve or migratory material, whilst in the case of 

 the cereal the crop is ripened, and its constituents are, there- 

 fore, more fixed. Further, whilst in the turnip-crop there 

 was several times as much dry substance in the roots as in 

 the leaves, in the barley there was even more dry organic 

 substance in the straw than in the grain. Again, in both 

 crops, by far the larger proportion of the dry substance con- 

 sists of carbodyrates — in the one chiefly sugar, and in the 

 other almost exclusively starch and cellulose — the latter mak- 

 ing up by far the greater portion of the dry substance of the 

 straw. It is obviously quite consistent that under these 

 circumstances there should be more of the total potash of the 

 barley crop accumulated in the straw than in the grain. It 

 must at the same time be observed that, whilst the potash 

 in the grain is comparatively fixed and bears a fairly uniform 

 relation to the amount of dry substance, the quantity which 

 remains in the straw is subject to great variation in propor- 

 tion to the dry matter, according to the variation in the 

 supply of it within the soil — a great excess above the amount 

 in other cases being sometimes found in the straw. Indeed, 

 the figures show a considerably greater proportion of the total 

 potash of the crop accumulated in the straw where there was 

 a liberal supply of it in manure. 



Keferring to the amounts of potash taken up in the rota- 

 tion barley crops on the different plots, according to the 

 manuring or other treatment, the figures show that there 

 was not much difference between the amounts without man- 

 ure and with superphosphate alone. There was, however, 

 distinctly more taken up on the portions of the superphos- 

 phate plot where the roots had not been removed than where 

 they were ; and where, therefore, there was conservation for 

 the succeeding crop. With the mixed manure, however, 

 with its supply of potash as well as of phosphoric acid and 

 nitrogen, the amount of potash in the crops is greatly in- 

 creased, the increase corresponding closely with the increased 

 amount of produce. * 



Lastly in regard to the potash, whilst without mauure and 

 with superphosphate alone the rotation barley has gathered 

 much more than the continuously grown, with the mixed 

 manure and full supply of all constituents, the amounts of 



