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of the aliment derived from all sources for that purpose. And, if 

 no other causes of destruction of fertility were in operation, one 

 green or manuring crop (wholly given to the land, and wholly used 

 as manure), would supply to the field as much alimentary or fer- 

 tilizing matter as would be drawn thence by three other crops 

 removed for consumption or sale. But in practice there are usu- 

 ally at work important agencies for destruction of fertility, besides 

 the mere supply of aliment to growing crops. Such agencies are 

 the washing off of soluble parts, and even the soil itself, by heavy 

 rains; the hastening of the decomposition and waste of organic 

 matter by frequent tillage processes and changes of exposure; and 

 ploughing or other working of land when too wet, either from 

 rain or want of drainage. Also, a cover of weeds left to rot on 

 the surface, or any crop ploughed under, green or dry, as manure, 

 is subject to more or less waste of its alimentary principles in the 

 course of the ensuing decomposition. Therefore, it is nearer the 

 facts that two years' crops or culture, for market or removal, would 

 require one year's growth of some manuring crop to replace, and 

 to maintain undiminished or increasing the productive power of 

 the field. The poorest, and also the cheapest, of such manuring 

 crops will be the natural or "volunteer" growth of weeds on lands 

 cultivated, and not grazed; and the best of all will be furnished in 

 the whole product of a broadcast sown and entire crop of your 

 own most fertilizing and valuable field peas. 



"Thus, of each manuring crop (as of all others), or of the fer- 

 tilizing matter thus given to the land, the cultivator has contributed 

 but five parts to the land, or its previous manuring, and the atmos- 

 phere has supplied fifteen parts. If, then, the cultivator, by still 

 more increasing his own contributions, will give ten parts of ali- 

 mentary matter to the land and crop, there will be added thereto 

 from the atmosphere in the same threefold proportion, or thirty 

 parts, and the whole new productive power will be equal to forty. 

 And if the soil is fitted by its natural constitution, or the artificial 

 change induced by calcareous or other applications, to fix and re- 

 tain this double supply of organic matter, the land will not only 

 be made, but will remain of as much increased fertility, under the 

 subsequent like course of receiving one year's product for manure 

 for every two other crops removed. But, on the other hand, if 

 more exhausting culture had been allowed, instead of either in- 



