408 Philosophy of Manures. 



Art. II. Further Ohservations on the Philosophy of Manures. 

 By R. Lyme URN. 



Since writing to you before, on the publications of Professors 

 Daubeny and Johnson on the subject of manures, there has 

 appeared a very able review of Dr. Liebig's work in the Qtiar- 

 terly Journal of Agriculture. The intimate knowledge displayed 

 of chemical action, and the cautious manner of applying it to 

 practice, I think, point out Dr. Madden as the author. The 

 reviewer, after giving great credit to the transcendent abilities of 

 Dr. Liebig, says that, nevertheless, his application of them to 

 practice has given great disappointment; and that old theories 

 must still be adhered to, till some more decided proofs of their 

 fallacy are brought forward. Dr. Liebig's statement, that humic 

 acid cannot yield the carbon necessary to plants, because of its 

 insoluble properties, he combats by stating Dr. Liebig's opinion, 

 that the ammonia so necessary to plants " passes through the 

 soil;" and he finds himself, by experiment, that neither am- 

 monia nor carbonate of ammonia can pass through soil without 

 combining with humic acid. All the ammonia must have reached 

 them, therefore, in combination with humic or some other acid; 

 and he thinks, therefore, the greatest part of the carbon of plants 

 is derived from the humate of ammonia. Wheat, he says, con- 

 tains 1 per cent of lime and alkalies; which, combined with 

 humic acid 10*9 grains, would yield 6*32 grains of carbon. It 

 also contains 2-13 grains of nitrogen, which, as humate of am- 

 monia, would yield 27'3 grains of carbon; in all, 33*62 per cent 

 of carbon, while the wheat itself only contains 43 per cent. Dr. 

 Liebig has forgot, he says, in his estimate of the quantity of 

 soluble humic acid in soil, which he states at less than 100,000th 

 part, that it is a substance constantly being produced, and con- 

 stantly taken up, and not a permanent ingredient in the soil. 

 In forty-two days, the time between the flowering and the ripen- 

 ing of the wheat, there will have been deposited in an acre of 

 wheat 500 lb. of carbon, equal to 877j lb. of humic acid, about 

 52VT P^''^ °^ ^^ weight of the soil, which the soil could not 

 have yielded at once, without the formation of humic acid were 

 a continuous one. He thinks all the humic acid in the soil at 

 one time will probably be consumed in ten days or a fortnight. 

 That neither humic acid nor humate of lime has been found 

 among the stalactitic formations of carbonate of lime in caverns, 

 he accounts for by saying that the humus is extricated from 

 the humate of ammonia in filtering through the soil, and de- 

 posited. 



Where such eminent men are at variance, it would be difficult 

 to decide. But, perhaps, it will not be of much consequence to 

 the practical man, whether the humus in the soil gives off its 

 carbon to the roots in the form of carbonic or humic acid. The 



