190 



THE SYSTEM OF FAKM-YAKD MANURING. 



A larger crop of any of the cultivated plants given 

 by one field over another merely indicates that the 

 roots in the one field in their way downwards, have 

 found and absorbed in certain portions of the soil more 

 particles of the whole store of nutritive substances con- 

 tained in it in an available state than the roots in the 

 other field ; but not that the total sum was greater in 

 the one than in the other: for the field apparently 

 poorer might in reality have contained a much larger 

 total amount of nutritive substances than the other, 

 only not in a condition available to the roots. 



High returns are a sure sign that the nutritive sub- 

 stances of the soil are in a condition available to the 

 roots ; the permanence of high returns, and that alone, 

 affords a safe criterion of the total store or quantity of 

 nutritive substances in the ground. 



The high returns yielded by one field above another 

 result from this, that the particles of the mineral con- 

 stituents lie nearer together in the one field than in the 

 other : they depend upon the closeness of the nutritive 

 substances. The following table may make this point 

 clearer : 



Cunnersdorf, Mausegast, Kotitz, Oberbobritzsch, Oberschona. 

 Fig. I. 1851. WINTER- RYE. 



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