214 [Senate 



once force themselves upon the mind. If a soil is barren, determine 

 its constituents — see what is wanting — what is in excess ; apply 

 at once the "deficient ingredient, or counteract or neutralize the inju- 

 rious one, and fertility is restored. A soil was shown to H. Davy, 

 which, though apparently abounding in every enriching material, was 

 incapable of yielding a crop. He found by examination, that it was 

 poisoned by a considerable portion of sulphate of iron or copperas. 

 He decomposed this sulphate by applying lime, and the difficulty 

 was removed. Here the remedy was simple and certain ; but such 

 cases very rarely occur in practice. 



As different plants draw from the soil the same substances in un- 

 like proportions, analysis of these plants will show which substances 

 are most largely needed for the different crops. And it points out a 

 reason of the fact, long since known, that a field which may bear a 

 profitable crop of one kind, may be unable to yield a good return of 

 another ; and that by alternation or rotation, different portions are 

 variously abstracted, and time left for the restoration of each by vari- 

 ous processes in nature, and by artificial means. But the fact that 

 these ingredients vary in the same plants, shows the great necessity 

 of caution in dra^ving practical conclusions. Justus Liebig, one of 

 the most eminent chemists of modern times, but whose deductions 

 are often deficient in value from a want of sufficient corroboration by 

 actual experiment in cultivation, says that one hundred parts of the 

 stalks of wheat yield 1.55 parts of inorganic constituents ; barley 

 8.54 parts ; and oats only 4.42 parts, all being of the same composi- 

 tion. " We have in these facts," he then adds, " a clear proof of 

 what plants require for their growth. Upon the same field which will 

 yield only one harvest of wheat, two crops of barley, and three of 

 oats may be raised." But every good farmer knows that oats is ex- 

 hausting to an extraordinary degree, instead of being less so than 

 barley, and only one third as much as wheat, according to this con- 

 clusion of Liebig. Some of the best farmers of New-York, never 

 suffer an oat crop to grow on land ever appropriated to wheat. Pro- 

 fessor Johnston has, however, demolished Liebig's reasoning, by 

 showing that these inorganic constituents are not only different in 

 composition, but greatly variable in quantity, the oats sometimes 

 considerably exceeding the barley, and the wheat varying from 3.5 

 per cent,, to 15.5 per cent. But neither of these chemists appear to 



