98 BRITISH PLANTS 



L. = A Leguminous Crop — e.g., clover, a deeply-rooting 

 plant, which is sown as a catch-crop. In a wet country 

 like ours it is not advisable to let the ground lie fallow 

 in order to allow time for nitrates to accumulate in pre- 

 paration for a crop demanding much of this salt, for the 

 frequent rains wash them out almost as soon as they are 

 formed. To obviate this, catch-crops like clover are put 

 on the land. Clover has bacterial nodules on its roots, 

 and if the crop is cut or eaten off the land, and not up- 

 rooted, it enriches the soil with nitrogen, and at the same 

 time consolidates it by its vegetable fibre and increases its 

 water-capacity. 



W. = Wheat, which is generally sown in autumn as 

 soon as the catch-crop is ploughed in. It is a deep- 

 rooted cereal, which makes a great demand on the soil 

 for silica and potash, as well as nitrates. It prefers a 

 rather heavy soil. 



R. = Root-Crops — e.g., turnips, swedes, etc. Two out 

 of the three preceding crops — viz., barley and wheat — 

 make exhausting demands upon the soU, and they foUow 

 so quickly upon each other that very few opportunities 

 are allowed to clean and prepare the ground thoroughly. 

 Root-crops, however, are not sown before the spring, and 

 this allows time for the land to be deeply ploughed and 

 cleared of weeds. Root-crops also require a good deal of 

 manure to encourage the production of large fleshy roots. 

 This is therefore the right time to add plenty of manure to 

 the soil, much of which will be available for succeeding crops. 



B.= Barley, a shaUow-rgoted cereal with similar de- 

 mands to those of wheat. Being a surface-feeder, barley 

 gets its nutriment from the upper layers of the soil, and 

 for this reason it follows the root-crop, while the ground 

 is still rich with manure. Wheat is a deep feeder, and 

 naturally foUows later, when the nutriment from the 

 manures has sunk deeper in the soil. On heavy soils oats 

 are generally substituted for barley. 



Different soils require different rotations, and agricul- 

 tural practices vary even on the same soils. 



Moreover, it has now been shown that rotation is not 

 really necessary to prevent the soil becoming impoverished. 

 With proper treatment and scientific manuring the same 

 crop may be taken year after year from the same ground 

 without diminishing its value. 



