J4 



AGRICULTURAL CHEMISTRY. 



culations that the basic metallic oxides 

 which have served to introduce humic acid 

 into the plants do not return to the soil, 

 since it is certain that they remain fixed in 

 the parts newly formed during the process 

 of growth. 



Let us now calculate the quantity of 

 humic acid which plants can receive under 

 the most favourable circumstances, viz. 

 the agency of rainwater. 



The quantity of rain which falls at Er- 

 furt, one of the most fertile districts of Ger- 

 many, during the months of April, May, 

 June, and July, is stated by Schubler to be 

 19.3 Ibs. over every square foot of surface ; 

 1 Hessian acre, or 26,910 square feet, con- 

 sequently receive 771,000 Ibs. of rainwater. 



If, now, we suppose that the whole quan- 

 tity of this rain is taken up by the roots of a 

 summer plant, which ripens four months 

 after it is planted, so that not a pound of 

 this water evaporates except from the leaves 

 of the plant ; and if we farther assume that 

 the water thus absorbed is saturated with 

 humate of lime (the most soluble of the hu- 

 mates, and that which contains the largest 

 proportion of humic acid ;) then the plants 

 thus nourished would not receive more than 

 330 Ibs. of humic acid, since one part of 

 humate of lime requires 2500 parts of water 

 for solution. 



But the extent of land which we have 

 mentioned produces 2843 Ibs. of corn (in 

 grain and straw, the roots not included,) or 

 22,000 Ibs. of beet root (without the leaves 

 and small radicle fibres.) It is quite evident 

 thdL the 330 Ibs. of humic acid, supposed to 

 bewbsorbed, cannot account for the quantity 

 of carbon contained in the roots and leaves 

 alone, even if the supposition were correct, 

 that the whole of the rainwater was ab- 

 sorbed by the plants. But since it is known 

 that only a small portion of the rainwater 

 which falls upon the surface of the earth 

 evaporates through plants, the quantity of 

 carbon which can be conveyed into them in 

 any conceivable manner by means of humic 

 acid must be extremely trifling, in compa- 

 rison with that actually produced in vege- 

 tation. 



Other considerations of a higher nature 

 confute the common view respecting the 

 nutritive office of humic acid, in a manner 

 so clear and conclusive that it is difficult to 

 conceive how it could have been so gene- 

 rally adopted. 



Fertile land produces carbon in the form 

 of wood, hay, grain, and other kinds of 

 growth, the masses of which differ in a re- 

 markable degree. 



2920 Ibs. of firs, pines, beeches, &c. grow 

 as wood upon one Hessian acre of forest 

 land with an average soil. The same super- 

 Gees yields 2755 Ibs. of hay. 



A similar surface of corn land gives from 

 19,000 to 22,000 Ibs. of beet root, or 881 Ibs. 

 of rye, and 1961 Ibs. of straw, 160 sheaves 

 of 15.4 Ibs. each, in all, 2843 Ibs. 



One hundred parts of dry fir wood con- 



tain 38 parts of carbon ; therefore, 2920 Ibj. 

 contain 1109 Ibs. of carbon. 



One hundred parts of hay,* dried in air, 

 contain 44.31 parts carbon. Accordingly, 

 2755 Ibs. of hay contain 1111 Ibs. of carbon. 



Beet rodts contain from 89 to 89.5 parts 

 water, and from 10.5 to 11 parts solid mat- 

 ter, which consists of from 8 to 9 per cent 

 sugar, and from 2 to 2 per cent, cellulai 

 tissue. Sugar contains 42.4 per cent ; eel 

 lular tissue, 47 per cent, of carbon. 



22,000 Ibs. of beet root, therefore, if they 

 contain 9 per cent, of sugar, and 2 per .cent 

 of cellular tissue, would yield 1032 Ibs. ol 

 carbon, of which 833 Ibs. would be due to 

 the su^ar, and 198 Ibs. to the cellular tissue; 

 the carbon of the leaves and small roots not 

 being included in the calculation. 



One hundred parts of straw,f dried in air 

 contain 38 per cent, of carbon ; therefore, 

 1961 Ibs. of straw contain 745 Ibs. of carbon. 

 One hundred parts of corn contain 43 parts 

 of carbon ; 882 Ibs must, therefore, contain 

 379 Ibs. in all, 1124 Ibs. of carbon. 



26,910 square feet of wood and meadow 

 land produce, consepuently, 1109 Ibs. of 

 carbon ; while the same extent of arable land 

 yields in beet root, without leaves, 1032 Ibs., 

 or in corn, 1124 Ibs. 



It must be concluded from these incon- 

 testable facts, that equal surfaces of cu.ti- 

 vated land of an average fertility produce 

 equal quantities of carbon; yet, how unlike 

 have been the different conditions of the 

 growth of the plants from which this has 

 been deduced! 



Let us now inquire whence the grass in 

 a meadow, or the wood in a forest, receives 

 its carbon, since there no manure no car- 

 bon has been given to it as nourishment ? 

 and how it happens, that the soil, thus ex- 

 hausted, instead of becoming poorer, be- 

 comes every year richer in this element ? 



A certain quantity of carbon is taken 

 every year from the forest or meadow, in 

 the form of wood or hay, and, in spite of 

 this, the quantity of carbon in the soil aug- 

 ments ; it becomes richer in humus. 



It is said that in fields and orchards all 

 the carbon which may have been taken 

 away as herbs, as straw, as seeds, or as 

 fruit, is replaced by means of manure ; and 

 yet this soil produces no more carbon than 

 that of the forest or meadow, where it is 

 never replaced. It cannot be conceived that 

 the laws for the nutrition of plants are 

 changed by culture, that the sources of 



* 100 parts of hay; dried at lOo" ^. (212 F.)and 

 burned with oxide of copper in a stream of oxygen 

 gas, yielded 51.93 water, 165.8 carbonic acid, and 

 6.82 of ashes. This gives 45 87 carbon. 5.76 hy- 

 drogen, 31.55 oxygen, and 6.82 ashes. Hay, dried 

 in the air, loses 11.2 p. c. water at 100 C. (212 

 F.) (Dr. Will.) 



t Straw analyzed in the same manner, and dried 

 at 100 C., gave 46.37 p. c. of carbon, 5.68 p. c. of 

 hydrogen, 43.93 p. c. of oxygen, and 4.02 p. c. of 

 ashes. Straw dried in the air at 100 C. lost 18 p. 

 c. of water. Dr. Will. 



