A MIXTURE SHOULD BE PREFERRED, 119 



ash contained in the crop, and the substances of which 

 it is composed, we can now understand why such small 

 quantities of these manures, seemingly thrown away 

 when spread over an acre of ground, should still con- 

 tain enough to supply all that is required by the plant 

 of their particular constituents. The largest crop of 

 wheat mentioned in Table viii, 54 bushels, would not 

 carry away in all of the grain more than 60 lbs. of ash, 

 and of this not more than 10 lbs. would be potash or soda. 

 We see, then, that the 1 cwt. of nitrate of soda sup- 

 plied enough of that material to have furnished at 

 least 150 bushels, and a large part of the straw beside. 

 The supplying of such minute quantities to the plant, 

 we have seen to be quite necessary, as much so as are 

 the bolts and nails to a ship: these are but a very 

 small part of its entire bulk or weight, and yet it could 

 not hold together without them. 



When the farmer intends to use any of these ma- 

 nures, it is in nearly every case better to make a mix- 

 ture. One hundred weight of nitrates of potash and 

 soda, of common salt, sulphate of soda and sulphate 

 of magnesia, all mingled together, and applied with a 

 few bushels of gypsum, would be much more likely to 

 meet the wants of any soil, than a hundred weight of 

 either one alone. Such mixtures are found remarkably 

 effectual, and they are the basis of the artificial ma- 

 nures now gradually coming into vogue. These ma- 

 nures are very excellent if the price is reasonable, and 

 the farmer assured of their purity. I have known 

 instances of most audacious cheating in these things, 

 and in a way too that could not readily be discovered 

 unless by a chemical examination. The farmer should 

 not buy these manures unless he has perfect confidence 

 in the manufacturers, or unless, as was recommended 

 with regard to guano, they furnish an analysis by com- 

 petent chemists, and warrant the manure sold to be 

 equal in quality. If it fails him, he can then have 

 compensation from them. 



