LIEEIG S MANURES. 



21 



The excrements of tlie latter contain the min- 

 eral elements of the leaves, stalks, and roots 

 in px-evailing qnantit}-. and have a greater 

 value for the production of roots and foliaceous 

 plants than those of man or of birds, which 

 contain only a small quantity of those mineral 

 substances which they require for theii- de- 

 velopment. 



If we compare, for instance, the composi- 

 tion of gixano with the excrements of the 

 cow — sohd and fluid excrements in the same 

 state of dr}Tiess — it is found, that in an equal 

 weight, the latter contain five to seven times 

 more of the mineral ingi'edients of ttu'nijjs 

 and potatoes than tlie former. If, in a soil 

 which is deprived of all those mineral sub- 

 stances, w^e wish to force a crop of turnips 

 by means of guano, we require at least five 

 times more of guano than dung of cattle. 



The same thing happens, though vice versa, 

 if we wish to produce a rich crop of grain by 

 means of animal excrements ; in this case, 

 one part of guano and live parts of animal ex- 

 crements, produce the same effect as tliirteen 

 to fifteen parts of animal excrements. 



To understand the proper meaning of these 

 numerical proportions, it is sufficient to men- 

 tion that 400 lbs. of bones contain as much 

 phosphoric acid as 1,000 lbs. of wheat ; these 

 400 lbs. of bones c;ui furnish sufficient phos- 

 phoric acid to eight acres. 



If we take the importation of bones into 

 Great Britain in the last ten years to amount. 

 to 1,000,000 of tons, enough phosphoric acid 

 has been supplied to the fields for 2.5,000,000 

 tons of wheat; but only a small proportion 

 of the phosphoric acid of tlie bones is in a 

 state to be assimilated by the plants and ap- 

 plied to the fonnation of grain. The plants, 

 in order to apply the other fai' gi'eater pait of 

 the phosphoric acid to their formation, must 

 find a certain quantity of alkaline bases beside 

 the bone-earth, wliich are not given to the 

 plants in the bones, because they contain 

 neither potash nor soda. 



To have increased the fertility of the fields 

 in the right proportion. 800,000 tons of potash 

 ought to have been added to the 1,000,000 

 tons of bones, in a suitable form. 



The same is the case w'lXh gnano : 60 to 

 100 lbs. of it are surticient to farni.^h phos- 

 phoric acid to one acre of timiips ; Ijut the 

 four to eightfold quantity is required to fur- 

 nish the turnips with tlie necessary alkaline 

 bases, and it is still doubtful whether they 

 can be at all provided with the latter, by 

 means of the salts with the alkahne bases, 

 which the guano contains. 



At a time when tiie necessity of the minenJ 

 substances for the gi-owth and development 

 of plants, and the dii-ect relation which the 

 effect of manure lias to its amount of the same 

 substances, had not l)een ascertained, a prom- 

 inent value was ascribed to the org;uiic mat- 

 ters which it contains. For a long time it 

 was thought that the produce of a field of 

 those substances containing nitrogen, which 

 serve as food for man and animals, stood 



(69) 



in a direct propoition to the nitrogen con- 

 tained in manure. It was believed that its 

 commercial value, or its value as manure, 

 might be expressed in per cents, by its pro- 

 portion of niti-ogen, but later and more con- 

 vincing observations have induced me to con- 

 tradict this opinion. 



If the niti'ogen and carbonic acid fonned by 

 the decay and decomposition of the vegetable 

 ingredients of manure were the cause of its 

 fertilizing power, this ought also to be seen if 

 the mineral suljstances were excluded. Di- 

 rect experiments have sliown that the nitro- 

 gen of the excrements can be assimilated bv 

 the plants in the form of ammonia, but that 

 ammonia, as well as cai'bonic acid, although 

 it is indispensable for the development of all 

 plants, can accelerate the growth of plants 

 and increase the produce of a field of gi'aui, 

 roots and tuliercles onlji, if, at the same time, 

 the mineral ingi-edients contained in the ma 

 nure which is applied, are in a state in which 

 they are suited for assimOarion. If the latter 

 are excluded, carbonic acid and ammonia 

 have no effect on vegetation. 



On the other hand, experience has shown 

 that on many fields produce which is rich in 

 carbon and ammonia, can be increased to an 

 extraordinary amount, without any supply of 

 such matters as furnish these substances. 



On fields w-hich are provided with a cer- 

 tain quantity of marl or slaked lime, or ^vith 

 bone-earth and gypsum — substances which 

 cannot give up to the plants either carbon or 

 niti-ogen — rich crops of gi'ain, tubers and roots 

 are obtained in many places, entirely in con- 

 tradiction witli the view which ascribes the 

 effect of the manure to its amount of ingi-e- 

 dients containing nitrogen or carbonic acid. 



To explain this process, which is so oppo- 

 site to the common opinion, the marl, the 

 lime, the gypsum, the alkalit-s and die bone- 

 earth were regarded as stimulants, wliich act- 

 ed on the plants like spices on the food of 

 man, of which it was believed that they in- 

 creased the power of assimilation, and allowed 

 the iuflividuals to consume lai-ger quantities 

 of food. 



This view is contradicted, if we consider 

 that stimulants mean such substances as do 

 not serve for the nourishment of the organism 

 or for the fonnation of organic elements, and 

 can only increase the weight of the body, 

 if at the same time a certain increase of food 

 is given. In supplying the fields with the 

 above mentioned suI)stancos, the weight of the 

 phmts became increased in all theii' separate 

 parts, without tlicir having been provided 

 witli the quantity of food which according to 

 theoiy, was necessaiy to this extraordinary 

 increase — viz., with cai'bonic acid and am- 

 monia. 



Chemical analysis shows that these so-called 

 stimulants ai-e either actual ingredients of 

 majiure, as gypsum, bone-earth and the active 

 subsUmces of the mad, or that they are the 

 means by which the mineral elements con- 

 tained in the soil ai-e resolved into a state 



