GREEN MANURING SUITABLE FOR AFTEH-CROPS OF CORN. 421 



IS sown for this purpose, being ploughed in before it begins to flower. 

 In French Flanders two crops ol' clover are cut^ and the third ploughed 

 in, and in some parts of the United States of North America the clover 

 which alternates with the wheat crop is ploughed in as the only ma- 

 nure (Barclay's "-Agricultural Tour in the United States.") White 

 Clover is not so valuable for this purpose, for neither is it so deep 

 rooted nor does it yield so large a crop of stems and leaves. 



9^. Old Grass. — Perhaps the most common form of green manur- 

 ing practised in this country is that of ploughing up grass lands of 

 various ages. The green matter of the sods serves to manure the 

 after-crop, and renders the soil capable of yielding a richer return at 

 a smaller expense of manure artificially added. 



In regard to all these forms of green manuring it is to be observed 

 that they enrich the soil generally, and are therefore well fitted to 

 prepare it for after-crops of corn ; they will not fit it, however, for a 

 special crop, such as turnips, which requires to be unnaturally forced 

 or pushed forward at a particular period of its growth. 



§ 4. Will green manuring alone prevent land from becoming exhausted? 



If by green manuring is meant the growing of vegetable matter upon 

 one field, and ploughing it in green into another, as is sometimes done, 

 it may be safely said that, when judiciously practised, land may by 

 this single process be secured for an indefinite period against ex- 

 haustion. But if we plough in only what the land itself produces, 

 and carry off occasional crops of corn, the time will ultimately come 

 when any soil thus treated will cease to yield remunerating crops. A 

 brief consideration of the subject will satisfy you of this. 



Suppose a loose sand to be improved by repeatedly sowing and 

 ploughing in crops of spurry or white lupins, the green leaves and stems 

 fix the floating elements of the atmosphere, and enrich the soil with or- 

 ganic matter, w^hile the roots, more or less deep, bring up saline matters 

 to the surface, and thus supply to the plant what is no less necessary to 

 its healthy growth. But the rains yearly wash away from the surface, 

 and the corn crops remove, a portion of this saline matter. This portion 

 the crops grown for the purpose of green manuring yearly renew by 

 fresh supplies from beneath. But no subsoil contains an inexhaustible 

 store of those saline substances which plants require. Hence, though by 

 skilful green manuring waste land may be brought to a remunerative 

 state of fertility, it will finally relapse again into a state of nature, if no 

 other methods are subsequently adopted for maintaining its productive- 

 ness. The process maybe a slow one, and practical men may be un- 

 willing to believe in the possibility of a result which does not exhibit it- 

 self within the currency of a single lease, or during a single life-time — 

 yet few things are more certain than that in general the soil must sooner 

 or later receive supplies of saline manure in one form or another, or 

 else must ultimately become unproductive. It may be considered as 

 a proof of this fact that, in all densely peopled countries in which 

 agriculture has been skilfully prosecuted, the manufacturing of such 

 manures has become an important branch of business, giving em- 

 ployment to many hands, and aflbrding an investment to milch capital. 



The folk wing table, in addit.:ni toother particulars, exhibits the 



