GREEN MANURES 115 



more important. Lands which, on the one hand, 

 are very hard and solid, with a tendency to bake, 

 and, upon the other, those which are loose and 

 leachy, are very greatly benefited by the addition 

 of organic matter. When this organic matter, as 

 animal and plant remains, decays and becomes 

 thoroughly incorporated with the soil, it forms 

 what is called humus. The addition of this 

 humus to the land makes it mellow, friable, 

 retentive of moisture, 'and promotes the general 

 chemical activities of the soil. It also puts the 

 soil in the best physical condition for the comfort 

 and well-being of the plants. Very many of the 

 lands which are said to be exhausted of plant- 

 food still contain enough potash, phosphoric acid 

 and lime, and other fertilizing elements, to raise 

 good crops ; but they have been greatly injured 

 in their physical texture by long -continued crop- 

 ping, injudicious tillage, and the withholding of 

 vegetable matter. A part of the marked results 

 which are obtained from the plowing under of 

 clover is due to the mere addition of vegetable 

 matter to the soil, wholly aside from the addition 

 of fertilizing material; and this is emphatically 

 true of clover because its deep -growing roots 

 penetrate and break up the subsoil. Muck and 

 leaf -mold are often very useful in ameliorating 

 either very hard or very loose lands. Excellent 

 humous material may be constantly at hand if 

 the leaves, garden refuse and some of the manure 



