36 



GAEDEXIXG FOR THE SOUTH. 



mits food-plants to grow, unless all the elements are with- 

 in their reach that are necessary to nourish and develope 

 the bodies of the beings that are to feed upon them. Those 

 manures are most valuable which furnish the materials 

 necessary for forming the azotized compounds required 

 for the food of man and animals. Hence the great value 

 of manures containing ammonia and the phosphates which 

 do not exist abundantly and are annually required and 

 taken away by the crops." (Balfour, Liebig.) 



" Alkaline and earthy phosphates form," says Liebig, 

 " invariable constituents of the seeds of all kinds of grass- 

 es, of beans, peas, and lentils." It is said, in the ash of 

 tea-leaves, they amount to 17 per cent. 



Bones, certain mineral substances, and the phosphatic 

 guanos, contribute to furnish the necessary supply. The 

 apparent effect of phosphates applied to the soil is to stim- 

 ulate vegetation and to promote the formation of roots. 

 If used for the drainage of pots in the form of broken 

 bones, or at the bottom of vine borders, the roots soon 

 find their way down to, and extract nutriment from them. 



The phosphates, like all other plant food, to be of ser- 

 vice, must be within the reach of the roots of plants. 

 Fertility is not to be measured by the quantity of plant 

 food a soil contains, but only by that portion which exists 

 in a finely divided state, as it is only with such portions 

 that the rootlets of plants can come in close contact. An 

 ounce of bone in a cubic foot of soil produces no marked 

 effect upon its fertility if unbroken. Dissolve it and let 

 it be distributed through the soil, and it will suffice for the 

 food of 120 wheat plants. The most abundant applica- 

 tion of earthy phosphates in coarse powder can, in its ef- 

 fects, bear no comparison with a much less quantity, 

 which, in a state of minute subdivision, is dispersed 

 through every part of the soil. A rootlet requires, where 

 it touches the soil, a most minute portion of food, but it 



