GEEEN MANUEING PLANTS 285 



to the habit of growth and the kind of root the grass 

 has. Some species require three or four, and in some 

 cases six years, to become firmly rooted and fixed in 

 the soil ; and they would, of course, be unsuited to 

 alternate husbandry. Among them may be named the 

 meadow foxtail and the June grass, and others of a 

 similar character will suggest themselves in studying 

 Chapter I. 



Again, some grasses have but a comparatively slight 

 hold upon the soil, .possessing few and bulbous roots, 

 which, when the soil- is -turned up, add but little to the 

 richness of the mould;' while others strike deep roots, 

 branching in every direction, and fill the soil with a 

 vast amount of vegetable matter, and add to its rich- 

 ness in decaying by the organic and inorganic matter 

 which they leave in it. 



This explains why clover is so valuable in alternate 

 husbandry, and how it enriches the soil, by mellowing 

 it in striking its long and deep roots into the subsoil, 

 by sheltering it from the scorching rays of the sun, by 

 drawing much of its nourishment and organic matter 

 from the atmosphere, and corporifying it, as it were, so 

 that whether it is turned under, if it is ploughed in 

 green, or its stubble broken up to give place to other 

 crops in the rotation, it leaves a large amount of valua- 

 ble matter to decay in the soil. The importance of 

 producing a large vegetable mass for the purpose of 

 ploughing in green as manure has already been alluded 

 to in another connection, and such grasses and other 

 plants suggested as will produce the greatest luxuriance 

 of growth, and add most to the vegetable mould in the 

 surface soil. The point is one of vast practical impor- 

 tance, and the practicability of a complete system of 

 green manuring ought to be tested by the most careful 

 experiments. 



