LIEBIG S MANURES. 



23 



in the first yeara, the produce of the soil had 

 increased by the application of bone ashes, 

 ■or by a single element of the manure — if this 

 increase was dependent on tlie amount in tlie 

 soil of the other mineral elements, a certain 

 quantity of those was annually taken up by 

 the plants and removed in the harvest, and a 

 time must at last arrive in which it is exhaust- 

 ed by the repeated removal ; the soil must 

 become bairen, because of all removed ele- 

 ments only one or the other, and not all of 

 them in a right proportion, have been re- 

 stored. 



The right proportion of the supply is, 

 however, the only true scientijic basis of Ag- 

 riculture. 



If we subject the fluid and solid excre- 

 ments of men and animals to an exact analy- 

 sis, and compare the elements of them ac- 

 cording to their weight, some constant rela- 

 tions between these elements impress them- 

 selves upon the muid, the knowledge of 

 which is of some importance. 



If the excrements of an animal are collect- 

 ed with some care and left to themselves for 

 some days, their nitrogen appears to have 

 been converted more or less perfectly into 

 ammonia. In the fluid excrements, in the 

 urine, the salts of the food, which are soluble 

 in water, are found in the fonn of alkaline 

 carbonates, or of sulphates, phosphates, and 

 other salts, with alkaline bases. In the solid 

 excrements or f;eces, silica, if it was contain- 

 ed in the food, earthy carbonates, and phos- 

 phates are the principal ingi-edients. 



The quantity of alkaline carbonates bears 

 a certain proportion to the amylum, sugar, 

 pectine, or gum of the food. The urine ot an 

 animal which has been fed with potatoes 

 or turnips, is rich in alkaline carbonates ; the 

 potatoes, however, consist principally of amy- 

 lum ; the chief ingredients of the turnips are 

 sugar and pectine. The urine of a hoi-se 

 w^hicli has been fed with hay and oats, is com- 

 paratively poor in alkalies, if compared with 

 the former. 



It is farther shown that the ammonia or 

 the nitrogen of the excrements bears a cer- 

 tain proportion to the phosphates ; the azote 

 increases or decreases with the quantity of 

 the phosphates in a manner that both can 

 serve as a measure for each other, although 

 not quite as an accurate one. It is not quite 

 accurate, because the gum and the amyliiin 

 also contain a certain, although small, quanti- 

 ty of phosphate of lime, as has been proved in 

 my laboratory. 



The ammonia of the excrements i.s of 

 cour.se derived from the nitrogenous sub- 

 fitances in the liwd : the phosphates are like- 

 wise constituents of the latter. In the com- 

 position of the food an equally constant pro- 

 portion exists between both. A given weight 

 of gluten or casein in peas or in grain always 

 corresponds with a certain weight of phos- 

 phates ; if the grain or the vegetable is rich 

 in these nitrogenous products of vegetable 

 life, it is also rich in phosphates ; if it is defi- 



(71) 



cient in them the quantity of the latter de- 

 creases in an equal ratio. 



As the amount of nitrogen in manure is a 

 measure for its amount of phosphates, and as 

 the manure contains besides these the other 

 ingredients of the soil w-hich are required by 

 the grain or by the other vegetables for their 

 development, and taken up by them from the 

 soil, it is easily conceived what was the 

 cause of the error in regarding the nitrogen 

 of the manure as the principal cause of its 

 eflicacy. The reason was, that the ammonia 

 of tlie manure is always accompanied by the 

 mineral elements which aflect its nourishing 

 qualities, because they render its assimilation 

 into the organism of the plant, and its transi- 

 tion into a nitrogenous constituent, possible. 

 Without phosphates, and without the other 

 mineral elements of the food of plants, the am- 

 monia exercises no influence whatever upoa 

 vegetable life 



If it has been shown that the fertility of 

 the soil depends on certain mineral sub- 

 stances ; if the restoration of the fertility of 

 exhausted fields by means of the excrements 

 of man and animals depends on their propor- 

 tions of these matters ; if the eflect of the 

 manures accelerating the vegetation depends 

 upon their proportions of ammonia, it is clear 

 that we can only dispense with the latter 

 when we provide all efficacious elements ex- 

 actly in those proportions and in that form 

 most proper for assimilation by the vegetable 

 organism in which they are Ibund, in the 

 most fertile soil or in the most efficacious ma- 

 nure. 



According to our present knowledge of the 

 effect of the constituent parts of manure, I 

 feel convinced that it is indifferent to the 

 plants from which source they ai-e derived. 

 The dissolved apatite (phosphate of lime) 

 from Spain, the potash derived fi-om felspar, 

 the ammonia from the gas-works, must ex- 

 ercise the same effects on vegetable life as 

 the bone-earth, the potash, or ammonia, 

 which we provide in manure. 



^Ve live in a time when this conclusion is 

 to be subjected to a comprehensive and ac- 

 curate trial, and if the result corresponds with 

 the expectations which we are entitled to 

 form, if the animal excrements can be re- 

 placed by their efficacious elements, a new 

 era of Agriculture must begin. 



I invite the enlightened farmers of England 

 to unite with me fir that purpose, and to lend 

 me their aid. Whatever may be the result 

 of these experiments, it is Hecessary for the 

 future prosperity of Agriculture that they 

 should be made. They will enrich us with 

 a number of valuable facts — we shall ascer- 

 t;iin where we have wasted efficacious mat- 

 ters in the common course of farming — we 

 shall ac(piire an exact knowledge ot those 

 substances which are necessary and of those 

 which are dispensable. 



For a number of years myself and many 

 talented young chemists have been occupied 

 with the analysis of those mineral substances 



