GUANO. 407 



cautiously on soils which contain but a small propor- 

 tion of vegetable matter, for fear that in the more rapid 

 decomposition which it stimulates, it may entirely 

 exhaust the soil of this material. If employed in such 

 cases it should be with admixture of vegetable matter, 

 that the loss which it occasions may be completely 

 replaced. 



1021. EFFECT OF ASHES ON SOILS. 



What other _ . . 



substances act Potassa or soda applied in the caustic state, 

 similarly? Qr ag car b ona t es have entirely analogous 



What caution 



is to be observ- effects on the soil. They render the in- 



edin their use? , , , .' 



soluble silicates soluble, by increasing in 

 them the proportion of base, and also hasten the decay 

 and conversion of vegetable matter. The admixture 

 of lime or ashes with guano or decomposed manure, is 

 to be avoided, because of their effect to expel the 

 ammonia which these substances contain. This may 

 be avoided by previously incorporating the material 

 with a large proportion of clay or vegetable mould, 

 which shall serve as an absorbent of the liberated 

 gas. 



What is said 1022. COMPOSTS. CompOStS COllsist of 



of composts? vegetable and other matter, heaped to- 

 gether for fermentation and partial decay, in order to 

 prepare them for application to the soil. In such mix- 

 tures, all alkaline materials, including lime, have an 

 effect similar to that which they produce upon the 

 organic matter of the soil. 



Whatisgua- 1023. GUANO. Guano consists of the 

 no? accumulated droppings of birds, and is 



principally obtained from certain rocky islands on the 



