EFFECT OF MINKKAT> M \Nn:r.S i!.7 



quarter plots wliieli are tallowed after the Itarlcy aetually grow 

 less than the correspoiuliiijj; uniiianiired plots. On these lattrr 

 plots the preceding growth of a comparatively large crop nf 

 roots has removed so nnich nitrogen that the s(.il is left jioorcr 

 than on the wdiolly unmanured plot, whicli lias Ikmmi laxr.l 

 less severely, though both are alike in receiving no supplv of 

 nitrogen during the whole com'se of the rotation. i^M.ni this 

 we may conclude that, in the absence of nitrogen, mineral 

 manm-es are of no use to the l)arley crop, the magnitude of 

 Avhich will depend on the amount of nitrogen available, even 

 when the mineral resom'ces of the soil have been considerably 

 drawn upon. In other words, with barley on unmanured land 

 nitrogen starvation sets in long before the deficit in minei-als 

 is felt, the reverse being the case with Sw^edes. 



Coming to the leguminous crop, the mineral maiuncs have 

 a very powerful effect, although they are applied a yeai- before 

 the clover is sown and two years before the crop is grown. 

 The increase brought about is from 9 to 33 cwt. of clo^ er 

 ha}^ and in the case of beans, from 157 bushels of corn and 

 87 cwl. of straw to 28*0 bushels of corn and 17 cwt. of 

 straws This illustrates well the generally accepted fact that 

 the leguminous plants are in the main independent of manurial 

 sources of nitrogen, which element they are able to draw fnjm 

 the atmosphere, especially when they are provided with ]»lenty 

 of mineral plant-food. 



In considering the wheat crop, it is necessary to distinguish 

 between the plots which have previously grown clover (.r beans 

 and those which have been fallowed, because in the foniHi- 

 case there has been such an accumulation of nitrogen in the 

 soil that the succeeding wheat crop is very much stimulated. 

 It will be seen that the crops on the fallowed portions 

 averaged about 32-4 bushels per acre, as against 271 bushels 

 per acre on the corresponding unmanured plots, an iiiei-ease 

 Avhich nuist in the main be set down to the niin.Tjj dressings 

 received three years earlier in the rotation. ^VIll'I•e clover or 

 beans are grown the crop mounts up to nearly H) bushels p<r 



