LIEBIG S MANURES. 



19 



which possesses no extension and gravity, no 

 effect can be produced, no burden raised. 



Guided by experience, which is the ttmda- 

 mental basis of all inductive science, and 

 which teaches us tliat for every effect there is 

 a cause, that every quality, as, for instance, 

 the fertility of a field, the nourishing quality 

 of a vegetiible, or tlie effect of a manure, is 

 intimately connected with and occasioned by 

 something which can be ascertained by 

 weight and measure ; modern science has 

 succeeded in enlightening us on the cause of 

 the fertiUty of the fields and on the effects 

 which are exercised on tlieni by manure. 



Chemistiy has shown that these properties 

 are produced by the composition of the fields ; 

 that their fitness for producing wheat or any 

 other kind of plant bears a direct proportion 

 to certain elements contained in the soil, 

 w^hich are absorbed by the plants. It has 

 likewise shown that two fields, of unequal 

 fertility, contain unequal (juautities of these 

 elements ; or that a fertile soil contains them 

 in a different fbnn or state from smother, 

 ^vhich is less fertile. If the elements are 

 contained in the soil in sufficient quantities, 

 it produces a rich crop ; if it be defective 

 even in one of them only, this is sliown very 

 soon< by tjie impossibility of growing on it 

 certain kmds of pkuits. 



Moreover, it has proved with certainty what 

 relations these elements of the soil bear to the 

 development of the plants. Chemical analy- 

 sis has demonstrated that a certain class of 

 these elements is contained in tlie seed* ; 

 others, in difl'erent proportions, in tlie leaves, 

 roots, tubers, stalks. They are mineral sub- 

 stances, and as such, are indestiiictible by 

 fire, and consequently remain as ashes after 

 the incineration of the plants or of their parts. 

 Many of these elements are soluble in }>ure 

 water, others only in water containing car- 

 bonic acid, as rain-water; all were al)soibed 

 fi'om the soil by the roots of tlie plants in a 

 dissolved condition. It has been shown that, 

 in a field, those elements which remain after 

 the incineration of the grain or seeds, are not 

 present in a sufficient quantity, no wheat, no 

 barley, no peas — in a word, none of tliose 

 plants can be cultivated on that field which 

 are grown on account of then- seeds. The 

 plants which grow on such a field jjroduce 

 stalks and leaves ; they blossom, but do not 

 bear fruit. Tlie same has been observed re- 

 garding the develo[)ment of leaves, roots and 

 tubers, and the mineral elements which tliey 

 leave behind after their incineration. If, in 

 a .soil in wiiich liiniips or potatoes are to be 

 cullivatcxl, the elements of the asfies of these 

 roots are wanting, the plants bring forth leaves, 

 stiilks, blos.-'oms and seeds, but the roots and 

 tubercles are imperfect. Evci-y one of tfie 

 elements which the soil gives up to the plants 

 is in a direct quantitative proi>ortion to the 

 production of the separate elements of the 

 plcUits. Two fields, wiiich, under otlierwiso 

 equal circumstances, are unequally rich in 

 muieral elements of the grain, produce une- 



(67) 



qual crops. One containing them in larger 

 quantity produces more than another con- 

 tainuig them in less. In the .same manner, 

 the capacity of a soil to produce tuberculous 

 plants, or such as have many leaves, depends 

 upon its amount of those elements wiiich are 

 feund in the aslies of such plants. , 



It results from this with certainty, that the 

 mineral substances which are furnishctl by 

 the soil, and which are found again in the 

 ashes of plants, are their true food ; that they 

 are the conditions of vegetable life. 



It is evident, that from a field in which dif- 

 ferent plants aie cultivated, we remove with 

 the crop a certain quantity of these elements; 

 in the seeds those mineral pai'ts which the 

 soil had to provide for their development, and 

 in the roots, tubercles, stalks and leaves those 

 elements which are necessary for their pro- 

 duction. However rich the field may be in 

 these elements, there can be no doubt that, 

 by several cultures, it becomes more and 

 more impoverished ; that for every plant a 

 time must arrive when the soil will cease to- 

 fiirnish, in sufficieiit (pinntity, those elements 

 whicli are necesiary for a perfect growth. 

 Even if such a field, during many years, 

 had produced twenty-five or thirt)' ibid the 

 amount of the seed, for instance, of wheat, 

 experience shows that the crop gradually 

 decreases, utitil at last ilie amount will be so 

 small as to approach the plant in its wild 

 state, and not repay the cost of cultivation. 



According to the unequal quantity in which 

 the mineral elements of graui, tubercles, roots, 

 seeds, leaves, are contahied in a soil, or ac- 

 cording to the proportions in which they 

 have been removed in the crop, the land 

 may have ceased to be fertile for i-oots and 

 tubercles, but it may yet produce go(jd crops 

 of wheat. Another may not produce wheat, 

 but potatoes and tuniips may thrive well in 

 it. The minend substtuices contained in a 

 fertile soil, and serving as food to the plants, 

 are taken up by them with the water, in 

 which they are soluble. In a fertile field 

 they are contained in a state which allows of 

 their being absorbed by the plant and taken 

 up by the roots. There are fields wiiich arc 

 rich in these elements, without being fertile 

 in an equal proportion; in the latter ciise they 

 iu-e united with other elements into chemi 

 cal compounds, which counteract the dissolv- 

 ing power of water. By tlie contemporane- 

 ous action of water and air — of the oxygen 

 and carlionic acid of the atmosphere — these 

 compounds are decomposed, and those of 

 their constituent elcMnents, which are soluble 

 in water, but which had been iiisolulile by the 

 cht^mical affinity of other other muieral sub- 

 stances, reobtain the property of being ab- 



I Borbed by tlie roots of the plants. 



The duration of the fertility of a field de-- 



I pends on tlie amount of the mineral aliments. 



I of plants contained in it, and its productive; 



j power for a given time is in a <iirect i)i()j)or- 

 tion to that part of its composition which pos- 



I sesses the capacity of being taken up by the 



