SECRETARY'S REPORT. 45 



THE APPLICATION OF MANURES. 



Fertilizers have a two-fold effect: nutritious effect on plants; 

 and the effect of modifying the soil. Certain substances are 

 essential to the growth of plants, which the manures must 

 furnish, if the soil is deficient in them. And these are all the 

 ingredients of plants, except silica and soda. Soil, however, is 

 seldom deficient in certain other substances, as iron, chlorine, 

 magnesia, lime. Whatever nutritious element of soil is deficient, 

 becomes most important in fertilizing. The absence of any one 

 essential ingredient renders the presence of all the others of no 

 account. Manure may act directly or indirectly, in the process 

 of feeding plants. The elements of manure may be taken up 

 at once by the plant, and may act precisely as the elements of 

 the soil, which are available to feed the plant. If we take a 

 barren soil, in which a plant will reach a small growth, the 

 addition of bone ashes or the ashes of wood will make the devel- 

 opment of vegetation luxuriant ; and if the quantity of these 

 fertilizing materials is properly chosen, we may prove by anal- 

 ysis of the plant that it has absorbed these matters almost 

 completely from the soil. This shows that under such circum- 

 stances the fertilizing matter passes at once into the plant. 

 Professor Wolff, of Hohenheim, prepared pots of calcined soil, 

 which alone would not support vegetation ; but by the addition 

 of salts of potash, lime, magnesia, phosphates, and salts of 

 ammonia, he rendered them capable of supporting clover vigo- 

 rously. 



Then there are manures operating indirectly by acting on the 

 soil ; not on the plant immediately. The application of lime, in 

 large doses, to soils already charged with lime, is beneficial in this 

 way: by acting on the soil it liberates matter already existing 

 there, but in an insoluble state. It would liberate the alkalies, 

 like potash ; and if long manured with animal manures it will 

 liberate the inert nitrogen. Lime often has the same effect as 

 guano, by liberating potash, as the solution of guano in the soil 

 does. The action of plaster and common salt is undoubtedly 

 owing to this indirect effect we speak of — the preparation of the 

 soil for nutrition. Recent experiments have demonstrated that 

 a solution of plaster liberates from many soils potash and mag- 

 nesia. It has been found by comparing tlie effect of pure water 



