614 The Lois Weedon Plan of Growing Wheat. 



parativclv small amount of nitrogen to the soil, in a form proved 

 to be readily accessible, can be of no avail, simply because the 

 soil itself already contains a much larger absolute amount ; — 

 though, from its distribution and state of combination, it may be 

 but in very small proportion available within a single season. 

 That soils are not necessarily more fertile because they contain a 

 larger actual amount of nitrogen, is interestingly illustrated in 

 the effects of burning clays. The burnt clay after some exposure, 

 as has been shown by Professor Voelcker, contains a much less 

 percentage of nitrogen than the unburnt. No doubt the in- 

 creased supply of available mineral food, as well as the change 

 of texture by which the roots of the plant, as well as the atmos- 

 phere, are enabled better to permeate the soil, have much to do 

 with the result. That this is so, may indeed be judged, by a 

 consideration of the descriptions of crop grown with most advan- 

 tage after the burning process. There can be little doubt, how- 

 ever, that the smaller amount of combined nitrogen, newly 

 acc{uired by the porous burnt soil, vvill be much more accessible 

 to the plant than the larger amount locked up in the unburnt 

 clay ; and to this circumstance, in all probability, a fair share of 

 the beneficial effects of burning should be attributed. In fact, 

 this smaller amount of accessible nitrogen in the exposed burnt 

 clay, has a much greater proportional effect as compared with 

 that in the unburnt, just as the smaller amount added in manure 

 in an available form has a striking effect in an ordinary soil, 

 notwithstanding that the latter may contain an enormously larger 

 amount, but in a less accessible condition. 



It is further, we think, very doubtful v/hether ordinary ac/ricul-' 

 turally cultivated soils, even contain^ in any form, so large an 

 amount of nitrogen as the uncritical reader might be led to sup- 

 pose from the statements on this point given by Baron Liebig in 

 the last number of this Journal. The percentages given in soils 

 by Dr. Krocker, w-hose figures Baron Liebig does not quote 

 in the Paper referred to, agree very closely in range with our 

 own experience in such matters.* Of those which he has now 

 brought more prominently forward, and which we have quoted 

 in full at an earlier page, the range is in some cases so high, and 

 the discrepancies between the individual analvses of the same 

 soil, as already shown, so great, thai we are disposed to place 

 much more confidence in the medium amounts given in that 

 Table. Then, again, neither the Russian black earth, nor the 

 soils of gardens or woods (the latter being the only ones given by 



* Dr. Krocker's results will be found in the Appendix to Baron Liebig's 4tl« 

 English Edition of his Chemistry in its Applications to Ag7-iculture and Physiology^ 

 p. 275. 



