SECRETARY'S REPORT. 47 



aged by these fertilizers, is correct. If plaster acts by liberat- 

 ing potash, its effect would not be manifest on a soil furnishing 

 an abundance of potash to the crops, and large doses of plaster 

 by increasing the solubility, already sufficient, might waste the 

 resources of the soil. 



Soils undergo modifications from year to year by tillage, 

 cropping, &c., and thus become subject to new requirements. 

 We often find a course of manuring which has been efficacious 

 for years lose its value and efficacy, and other fertilizers that 

 had been in disrepute are found to be advantageous. On the 

 shores of Long Island Sound fish have long been employed, 

 and have at last proved to have lost their beneficial effects, and 

 on such lands super-phosphate of lime has operated witli good 

 effect. 



Generally such partial fertilizers as fish, guano, lime, and 

 plaster, are liable to fail after many years and something else 

 is necessary. 



Peculiarities of the plant also influence the action of fertili- 

 zers. Much experience seems to prove that turnips are specially 

 fond of super-phosphates. Clover grows readily after an appli- 

 cation of ashes or plaster, a fact accounted for, perhaps, by the 

 supply of potash which they give. 



Waste of Manures. — Manures may be lost by direct washing 

 or leaching. The most precious ingredients of manures are. 

 wasted in this way — such as potash, plrosphoric acid, and 

 ammonia. Salts of lime and soda, especially sulpliates and 

 chlorides, are readily washed out ; hence they are found in all 

 well-waters. The loss by leaching is, therefore, small, except 

 in the lightest and gravelly soils. 



By chemical change manure may be lost, or become inactive. 

 Bousingaiilt found that in the soil of his garden, which had 

 been highly manured for about six centuries, and which con- 

 tained a large proportion of nitrogen, about ninety-six per cent. 

 of this ingredient was inactive. He limed his garden, and thus 

 rendered a portion of this nitrogen active. When fertilizers are 

 placed beyond the reach of oxygen, by being buried deeply in 

 heavy soil, the chemical changes necessary to render them 

 operative are entirely suspended. 



Loss hy Volatilization. — There need be none, if manures 

 are properly prepared and judiciously applied. Fresh manure 



