The Lois Weedon Plan of Growing lllieat. 615 



Baron Liebig as analysed by himself), can be taken as parallel 

 ■with ordinary farmin2:-land, under ordinary cultivation. 



With re<jard to any estimates that mig-ht be made from our 

 own determinations of nitrojjen in the soils at Rothamsted and 

 Lois Weedon, of the probable acreage amount within a given 

 depth, it may be observed, that the result obtained and published 

 ten years ago of the amount of nitrogen in the soil of our conti- 

 nuously unmanured wheat plot (0'2 p. c), was considerably 

 higher than that now recorded in Table IV^. This was to a great 

 extent due to the fact, that the earlier sample was taken to little 

 more than half the depth of the recent one. By reference to the 

 analysis book we also find that, for a substance containing so small 

 an amount of nitrogen, much too small a quantity was submitted to 

 analysis. Tiiere is also the consideration, whether or not part of 

 the difference is due to the reduction of the condition of the land in 

 regard to nitrogen, by the removal of ten more unmanured wheat 

 crops. It is clear, however, that the determination of nitrogen made 

 upon a sample taken to only half that depth, cannot be taken in 

 estimating the probable acreage amount to the depth of one foot. 

 Then, again, since the analyses now recorded were made upon 

 samples taken to the depth of only nine inches, the calculated 

 acreage amounts one foot deep, given in the lower part of 

 Table IV. for comparison with Baron Liel)ig's adopted depth of 

 one foot, must obviously be too high. With these explanations, 

 then, as to the degree of applicability of our figures to any esti- 

 mates of acreage amounts, the results are committed to the reader, 

 as some additional data on the many points of interest which this 

 fjuestion of the nitrogen in soils involves. 



It was our hope and intention, had our time permitted it, to 

 have included within the limits of this paper a short review of 

 existing knowledge, and especially of the results and tendency 

 of the investigations of recent times, bearing upon the sources of 

 availal)le nitrogen to cultivated plants, l)oth within and without 

 the soil. It is, indeed, remarkaljle how many are the inde- 

 pendent researches, Irom experimenters both numerous and 

 Aaried in their pursuit and oljject, which have come in upon tliis 

 fiekl of inquiry during the last few years. It is not less remark- 

 able, that the subject of agricultural chemistry, perhaps more than 

 any otlier, has demanded and successfully incited a rigid investi- 

 gation of methods of research ; and it has, both in this country, 

 in fiermany, and in France, led to improvement, and a much 

 greater degree of accuracy, in some of the most dithcult depart- 

 ments of chemical analysis. Besides the estal)lishment of 

 methods for tlie determination of quantities of ammonia and 

 nitric acid, formerly far too minute to be made tlie suhject of 

 successful quantitative estimation, the analvsis of gases, the 



