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 soil, and they follow 
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 shallow-rooted 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 follows 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. 
