J. B. LAWES AND JUSTUS VON LIEBIG. 



273 



yielded 18 tons, 1 cwt of turnips, six tons more than 

 those fields on which phosj)horic acid was employed. 

 * * What strange results do these facts offer, — in 

 what incomprehensible contradiction do they stand 

 to the views of Mr. L.\wes." On referring to our 

 copy of Mr. Lawes' opinion, we found a marginal 

 note, made years ago, stating that the 18 tons, 1 cwt., 

 should be 10 tons, I cwt. It is much to be regret- 

 ted that this mistake was not marked in the copy sent 

 Professor Liebig; or that he did not discover the 

 error, as he might have done by referring to the ta- 

 bles on the two following pages. Few will be sur- 

 prised, considering the immense amount of tabulation 

 in Mr. L.iwes' papers, that a printer should, in one 

 instance, place an 8 instead of 0, but it will astonish 

 many to find that on this single mistake, Liebio 

 should adopt a view which is not only opposed to the 

 general indications of the whole series of experiments, 

 but is also at variance with the experience of every 

 farmer who has used superphosphate of lime and sul 

 phate of lime as a manure for turnips. 



This error corrected, the opinion based upon it falls 

 to the ground, and with it the idea that the beneficial 

 effect of sulphate of ammonia on wheat is due to its 

 rendering the phosphates of the soil soluble. Solu 

 ble phosphates greatly increased the turnip crop, but- 

 the same soluble phosphafcs, on similar soils, did not 

 increase the wheat crop; sulphate of ammonia did 

 not increase the turnip crop, but did greatly increase 

 the wheat crop; therefore, sulphate of ammonia docs 

 not act simply in furnishing to the wheat plants solu- 

 ble phosphates. 



Mr. Lawes repeatedly alludes in his papers to the 

 I fact that though the increase of wheat over the un- 

 manured plot was in pretty direct ratio to the quan- 

 tity of ammonia supplied to the soil, yet that the in- 

 crease was never so great as theoretical considerations 

 would lead us to suppose. Thus, estimating a bashel 

 |( of wheat and its proportion of straw, to contain a 

 pound of nitrogen, it might be supposed that if ni- 

 trogen was wanted, a pound of nitrogen, applied in 

 soluble ammonia salt, would give an extra bushel of 

 wheat; but this is not the case. Without making 

 any pretensions to settle the exact amount, Mr. 

 Lawes estimates from the immense number of instan- 

 ces in which ammonia has been used, in various ways 

 and proportions, in his experiments, that five times as 

 much nitrogen, in the form of ammonia, is required 

 to produce a bushel of wheat, as it contains when 

 grown. This estimate has stood the test of many 

 trials, and is in accordance with the well-ascertained 

 efiects of Peruvian guano on v;heat Mr. Lawes 



founds on this fact some very important practical 

 suggestions, but which we cannot at this time refer 

 to. Liebio takes no notice of this opinion, and refers 

 to the loss of ammonia in these experiments, as 

 though it had escaped the attention of Mr. Lawe.s, 

 and as though he were the first to point it out; and 

 he proceeds to show that the increase "bears no re- 

 lation whatever^' to the ammonia added to the soil. 

 This is proving far too much, even for Liebig's own 

 theory of the action of ammonia as a solvent; but let 

 that pass. The method Liebig adopts to get at this 

 result, is as follows: 60 lbs. of ammonia, say, give in 

 1844, an increase on the unmanured plot of 10 bush- 

 els. This increase only contains 15 lbs. of ammonia, 

 and therefore Liebig estimates that " beyond all 

 doubt," 45 lbs. of ammonia are left in the soil for the 

 next crop. In 1845, 60 lbs. of ammonia again give 

 an increase of 10 bushels, but Liebio adds to this the 

 45 lbs. which he assumes remain in the soil from the 

 previous year, making 105 lbs.; and in this way he 

 proceeds, adding the ammonia he supposes to remain 

 in the soil to that applied each year, and from the fig- 

 ures obtained, proves that the increase bears no pro- 

 tion to the supply of ammonia! We believe this 

 method of estimating the action of ammonia, funda- 

 mentally erroneous. Certainly we do not know of a 

 single result in these or any other experiments, that 

 shows th^ ammonia of soluble salts to remain in the 

 soil over one year, when wheat is grown, and when 

 sufficient minerals are present to enable the plants to 

 take up all the ammonia they require. Let us sup- 

 pose a case, and one which is clearly deducible from 

 the experiments. The continuously unmanured plot 

 gives 15 bushels of wheat per acre; a plot adjoining, 

 dressed with 30 lbs. of ammonia, gives 20 bushels 

 per acre; another lot dressed with 60 lbs. of ammo- 

 nia, gives 25 bushels; another dressed with 90 lbs., 

 gives 30 bushels; and another receiving 120 lbs., 35 

 bushels per acre. The next year, all these plots re- 

 ceive no manure, and the produce is the same on each, 

 neither more nor less than that from the continuously 

 unmanured plot. What deductions should we make 

 from such facts? According to Liebig's view, the 

 first plot would contain, the second year, no ammo- 

 nia; the second plot would contain 24 lbs. of ammo- 

 nia; the third 48 lbs., the fourth 72 lbs., and the fifth 

 96 lbs. of ammonia per acre. Now if this be true, 

 surely the produce would not be alike -on all the 

 plots. A direct application of ammonia has always 

 given a definite increa.se, and we cannot see why the 

 ammonia remaining in the soil from the previous year 

 should not also give an increased yield. The fact 



