56 ON INCREASING THE GROWTH 



narily rapid operation and forcing power observed in 

 manuring with guano, soot, gas-water, drainings, or 

 ammoniacal salts (sal-ammoniac, carbonate or sul- 

 phate of ammonia), is thus explained at once; all 

 these substances contain ammonia ready made. 



That putrid nitrogen or ammonia really consti- 

 tutes the " forcing " element in guano and in other 

 composts, the farmer may very readily convince him- 

 self by a few extremely simple experiments. A 

 goodly number of plants with red leaves is often 

 found in fields of rape or beet-root, chiefly in those 

 places where the soil lacks power ; for example, in 

 the furrows and head-lands. If a few red leaves of 

 this description are put into a tumbler with water, and 

 a teaspoonful of hartshorn poured on in addition, a 

 change of color will soon become evident ; and in a 

 few minutes the leaves will have become dark-green. 

 It is the ammonia of the hartshorn which converts 

 the hungry red color into satisfied green ; for water 

 alone produces no such change, and except this 

 (and ammonia) no constituent elements are present 

 in the hartshorn. The same alteration will be man- 

 ifested if a quart of water to which one table-spoon- 

 ful of this fluid (or one quarter of an ounce of any 

 ammoniacal salt) has been added, or, again, a quan- 

 tity of putrid drainings, or a weak solution of guano, 

 is poured upon those patches of ground where the 

 red leaves in question are produced. These experi- 

 ments show very plainly what is wanting to the 

 soil ; the farmer says it is destitute of power, and the 



