330 MANURES. 



Ibs. of sulphate of ammonia. The extra 15 bushels con- 

 tain about 18 Ibs. of mineral matter more, which was sup- 

 plied by the manure, and this is equal to one and a half 

 year's supply for the natural crop of the land. The effect 

 of this sort of farming is that the soil is made to produce 

 more than it can afford to in one year, and has its supply of 

 mineral plant food exhausted to the detriment of its future 

 productiveness. 



Twenty years ago, the wheat lands of Delaware, which 

 had been producing very small crops, were made, by the 

 use of very small doses of Peruvian guano, to double, triple, 

 even quadruple their yield. The farmers were immensely 

 elated. They had found a sort of philosopher's stone, and 

 a few years would make their fortune. Alas for their hopes 

 a very few years demonstrated the fact that the guano had 

 been a curse rather than a blessing. Their lands were poorer 

 than ever, and even largely increased doses of the specific 

 were powerless to bring them up even to their old stan- 

 dard. 



Had the wheat and straw been consumed on the farm, 

 and all of their mineral constituents returned to the soil, 

 the guano would have been a means of great permanent 

 improvement. 



Or, had the same increase of production been effected by 

 the use of a manure containing the full equivalent of what 

 the crop was to take from the soil, the impoverishment of 

 the land would have been prevented. 



