108 
Ploughing-in Green Crops. 
and gave it back in the same state of cliemical combination in 
which they drew it forth, they Avould affect the soil none other- 
wise than by the accidents of their culture. But by far the largest 
portion of their bulk is derived, not from the soil at all, but from 
air and water, and the whole of this is contributed by green manure 
as clear gain preparatory to the succeeding crop ; whilst the re- 
maining portion, though extracted from the soil, is brought into 
new affinities, assuming more available forms than before, so that 
even this, as returned to the soil by green manure, is in a more 
advantageous condition for rapid assimilation than if it had not 
recently played a part in vegetable growth. The plants most 
appropriately employed for green manuring are those that derive 
their support principally from the air. As the organic portion 
of these plants decays in the soil, the inorganic part — that is, 
saline and earthy matter, of which all vegetables contain a con- 
siderable quantity — is liberated. Thus living plants obtain from 
the remains of former races buried beneath the surface, a portion 
of that inorganic food which can only be derived from the soil, 
and which, if not thus directly supplied, must be sought for by 
th(! slow extension of their roots through a greater depth and 
breadth of the earth in which they grow. The addition of 
manure to the soil, therefore, places within the easy reach of the 
roots, not only organic, but also inorganic food. 
The use of green manure, though a very important and powerful 
means of enriching the soil, and though known and practised by 
very many farmers of the present day (in marshland), has received 
surprisingly little attention from scientific agriculturists. Among 
the farmers, generally, residual green manure from cultivated 
plants is known principally in the form of clover ploughed up. 
Old pastures, moreover, when broken up and converted into 
arable, prove abundantly that the soil has been enriched, not 
only by the death and slow decay of bygone plants, but that the 
leaves and roots of the grasses, living at the time, afford by their 
gradual decomposition an immediate supply of food for cereal 
crops for a succession of years. 
The chief causes of the neglect of green manure are, — 1st, the 
want of a due appreciation of its value ; 2nd, the lateness of the 
harvest and consecjuent slowness of growth between the time of 
sowing the seed and that of ploughing-in the crop ; and 3rd, 
the carrying out to an unwarrantable extent the principle that 
green vegetable substances, to be profitably employed as manures, 
ought to be in the first place used as food for animals. 
The use of special green manure can never supersede the 
necessity for farmyard manure ; yet it is a resource of great 
value in all situations where ordinary manures are scarce or 
very expensive, and is peculiarly applicable upon stiff-clay soils. 
