59G The Lois Weedon Plan of Growing Wheat. 



which, he says, should satisfy living man. And it should be 

 borne in mind, that the resources of the soil are not to be spoken 

 of, as some are wont to do, as sufficient for — say fifty or a hun- 

 dred crops, and to be cleared off to the zej'o point at pleasure, in 

 half or double the number, accordingly as the soil is supplied with 

 other elements of growth. Whatever the actual stores of the soil, 

 they are only little by little available ; and it is not easy to sup- 

 pose that a heavy soil, yielding, under proper management, 

 annually enough for large crops over a continuous series of 

 years, does not contain a correspondingly enormous store in the 

 dormant state. Whether, however, the same soil would annually 

 yield an equal supply of available minerals if its surface were 

 less exposed to weathering influences, and the required nitrogen 

 for full crops were provided by manure, is quite another 

 question. 



But now let us turn, as briefly as possible, to a consideration 

 of the nature of the evidence which analysis affords, of the 

 amount of nitrogen contained in soils, and then, equally briefly, 

 to a review of some of the circumstances which seem to have 

 their share in the production of the large annual crops of wheat, 

 without manure, at Lois Weedon. 



As is well known, in 1843 Baron Liebig laid more stress than 

 formerly on the sufficiency of the assimilable supplies of nitrogen 

 in the atmosphere ; and a few years later, after having before 

 him the analyses of a number of soils made in his laboratory by 

 Dr. Krocker, he superadded to the argument of the inexhausti- 

 bility of the supplies of the atmosphere, that of the large amount 

 of nitrogen contained in soils themselves, to show that little or 

 no effi?ct could be attributed to the small proportion which is 

 added in an ordinary dressing of manure ; and to this he now 

 adds, still more emphatically, in reference to fallow, that the accu- 

 mulation of ammonia in the soil in one year has no influence on 

 the crop in the succeeding year. With regard to the amount of 

 nitrogen in the soil, we, in 1847, alluded to this point, and gave 

 the percentage obtained by analysis of the surface-soil of the 

 field upon which our experiments on wheat were being con- 

 ducted. The necessary distinction to be drawn between the im- 

 mediately available and the actually existing contents of the soil, 

 as above referred to, was, however, too obvious to allow a mo- 

 ment's scepticism as to the influence of the small proportions of 

 available nitrogen which, in our experiments, we superadded in 

 manure. On this point, however, as it is very important to the 

 farmer that he should be satisfied respecting it, we cannot do 

 better than quote the replies to this argument of Baron Liebig 

 by M. Boussingault, and by M. Kuhlmann ; to the latter of whom 

 Baron Liebig dedicates the fuller version of his paper in the 



