602 The Lois Weedon Plan of Growing Wheat. 



by the current methods. We may say, however, that every pre- 

 caution has been taken to secure as much of accuracy as those 

 inethods are capable of. Nor are we wanting in evidence in the 

 results themselves, that within certain limits, and for the discus- 

 sion of some points of comparately broad distinction, they are 

 sufficiently conclusive. 



In the following Table (IV.) are given the results of deter- 

 minations of nitrogen — in the soil and subsoil of the plot devoted 

 at Rothamsted to the experiments on the Lois Weedon system — 

 in the soil of the continously unmanured plot, of the continu- 

 ously mineral-manured plot, of the continuously ammonia- 

 manured plot, and of the continuously mineral and ammonia- 

 manured plot, in the adjoining experimental wheat-field. There 

 are also given, the determinations of nitrogen in specimens of 

 soil and subsoil, &c., from the Rev. Mr. Smithes .experimental 

 fields at Lois Weedon. And, for the sake of comparison with 

 the figures in Table ITI. last discussed, there is given in the lower 

 portion of the lable (IV.), the amounts of nitrogen (in lbs.) that 

 would be contained in 4,000,000 lbs. (= an acre about a foot 

 deep) of the specimens analysed — both according to the individual 

 analyses, and to the mean result for each specimen. In the last 

 column, the mean acreage amount of nitrogen is represented in its 

 equivalent amount of ammonia. It is obvious, however, that no 

 actual fact is represented by thus applying the analyses of soils 

 and subsoils indiscriminately, to a supposed equal acreage weight 

 of soil in each case. The figures are only useful*as conveying 

 a very general comparative idea, of about how much ammonia, 

 or its equivalent of nitrogen, would exist in a layer of one acre 

 area, and about afoot thick, of soils or subsoils containing a given 

 percentage amount. 



It must be remarked, too, that whilst the specimens of sur- 

 face-soils at Rothamsted were each taken at eight different 

 nlaces, and as nearly as possible to a depth of nine inches and 

 an area of a foot square, the whole being then well mixed and 

 re-sampled, those at Lois Weedon were each taken at one spot 

 only ; a good spit of depth being the only condition attended to. 

 The soils at both places were collected during the present year 

 (1856) ; those at Lois Weedon in August, and most of those at 

 Rothamsted in September. 



In all cases the soils Avere broken up and turned over and the 

 large stones picked out ; they were then further reduced and 

 separated from smaller stones. Finally, they were rubbed to 

 fine powder and passed through a fine sieve, in which state 

 they were submitted to analysis. In these processes of prepara- 

 tion the soils were never submitted to a temperature above 60^ to 

 70° F., and when so prepared they generally retained less, or little 



