100 



THE EOTHAMSTED EXPEKIMENTS. 



Root-range 

 of wheat. 



Barley a 

 surface- 

 feeder. 



Manures 

 requisite 

 for wheat 

 and barley. 



Soils for 

 wheat and 

 barley. 



heavier soil, and has four or five months in which to dis- 

 tribute its roots, and so gets possession of a wide range of soil 

 and subsoil, before barley is sown. 



Barley is sown in a lighter surface-soil, and, with its short 

 period for root-development, relies in a much greater degree 

 on the stores within the surface-soil. Accordingly, it is 

 more susceptible to exhaustion of surface-soil as to its nitro- 

 genous, and especially as to its mineral, supplies; and in 

 the common practice of agriculture it is found to be more 

 benefited by direct mineral manures, especially phosphatie 

 manures, than is wheat when sown under equal soil conditions. 



The exhaustion induced by both crops is, however, char- 

 acteristically that of available nitrogen; and when, under 

 the ordinary conditions of manuring and cropping, artificial 

 manure is still required, nitrogenous manures are, as a rule, 

 requisite for both crops, and for the spring-sown barley, 

 superphosphate also. 



Lastly, although barley is appropriately grown on lighter 

 soils than wheat, good crops, of fair quality, may be grown 

 on the heavier soils after another grain crop, by the aid of 

 artificial manures, provided that the land is sufficiently clean. 



SECTION III.— EXPERIMENTS ON THE GROWTH OF VARI- 

 OUS LEGUMINOUS CROPS FOR MANY YEARS IN 

 SUCCESSION ON THE SAME LAND; ALSO ON THE 

 QUESTION OF THE FIXATION OF FREE NITROGEN. 



Character- 

 istics of 

 different 

 crops. 



Introduction. 



We now come to the third element of the ordinary four- 

 course rotation — namely, Leguminous Crops, which, indeed, 

 have a place in most other rotations also. 



It is found that, within certain limits, the requirements, 

 and the results of growth, of different members of one and 

 the same family show certain characteristics in common ; 

 whilst those of different families show more or less of dis- 

 tinctive character. Nevertheless there are some important 

 points of similarity, as well as of contrast, between the re- 

 quirements of the agricultural representatives of the Gra- 

 minese, the Cruciferse, the Chenopodiaceee, and the Solanese. 



It will be seen, however, that the agricultural representa- 

 tives of the Leguminosse, all of which are included in the 

 sub-order Papilionacese, and some of which are of much im- 

 portance in our agriculture, show very marked differences as 

 compared with those of any of the other Orders above 

 enumerated. 



