ROTATION OF CROPS. 241 



potash taken up were, as were those of nitrogen and phos- 

 phoric acid, nearly the same in the rotation and the continu- 

 ous crops where in rotation the preceding roots had not 

 been removed ; but where they had been removed, the amounts 

 of potash in the succeeding barley were less, as were the crops 

 themselves. 



The Potash in the Leguminous Crops. — Of all the mineral 

 constituents of the crops, perhaps potash and lime are the 

 most generally recognised as having some distinctive effects 

 when applied as manure for leguminous crops. We have now 

 to refer to the records relating to the potash in these crops, 

 as given in the third division of Table 64. 



The figures show that, in the case of the beans, unlike that Potash in 

 of the cereals, there is much more potash in the corn than in c ° rn an j 

 the straw ; indeed, more than twice as much of the potash of legumes. 

 the crops was accumulated in the corn as in the straw ; indi- 

 cating, therefore, a special requirement of it for the formation 

 of the final and most fixed product of the plant — the seed. 



Looking to the amounts of potash per acre in the total pro- Effects of 

 duce, corn and straw together, of the rotation beans, it is seen manure$ - 

 that they take up very little more under the influence of the 

 superphosphate than without manure ; the quantities averag- 

 ing about 10 lb. per acre without manure, and scarcely 12 lb. 

 with superphosphate. With the mixed manure, however, 

 directly supplying potash for the previous root-crop, the 

 amounts of it taken up were, in the one case 22.16, and in the 

 other 24.46 lb., or about twice as much as with the super- 

 phosphate alone. The influence of the previous supply of 

 potash on the amounts of it taken up in the beans was, in 

 fact, much greater than was that of the supply of phosphoric 

 acid on the amounts of it taken up. 



But, as in the case of the phosphoric acid, so also in that of Rotation 

 the potash, the continuously grown beans took up only about °^ s c ^ 1 ^' 

 half as much as those grown in rotation ; proportionally more, 

 however, where it had been supplied than where it had not. 

 It will be remembered that, when discussing the amounts of 

 produce of the bean crops, attention was called to the fact 

 that throughout the experiments a really good agricultural 

 crop was scarcely ever obtained ; and this of course must be 

 taken into account when considering the amounts of the 

 several constituents of the crops. 



Comparing the amounts of potash stored up in the rotation Clover and* 

 clover with those in the rotation beans, it is seen that, even be %™ d com ~ 

 without manure and with very small produce, the clover, with 

 its greater root- range and longer period of growth, gathered 

 up about three times as much potash as the beans — about 

 30 lb. against only about 10 lb. in the beans. 



VOL. VII. Q 



