THK BKOAD1JALK WHEAT SOILS. 
25 
SAMPLES TAKEN IN 1893. 
These samples, you may be reminded, wciv drawn at the close of 
the fiftieth experimental year of continuous wheat growing on the 
same series of plats. As the results of the examination of this series 
of samples are sew, and as they possess, od account of the greater 
age of the experiments, more interest than the earlier samples, they 
may be allowed to have the first claim on our attention. They will 
subsequently be considered in relation to those of the earlier samples. 
TOTAL NITROGEN AND ORGANIC CARBON (GENERAL DISCUSSION 
AND FULL STATEMENT OF ANALYTICAL RESULTS). 
The most Important element in the soil, because the most expensive 
one to supply, and therefore the one we are most anxious to conserve, 
is the nitrogen. We will, therefore, consider in the first place the 
results of the determinations of nitrogen in the samples representing 
the soils and subsoils of the various plats. 
It is here necessary to explain to those who are not practical chem- 
ists that there are two methods in general use for the determination 
of nitrogen in such bodies as soil. .Much the older, and formerly the 
almost universally adopted, method was that known as the soda-lime 
combustion method. All the earlier determinations at Rothamsted 
were made by t his method of analysis, in the last few years another 
method, one of •'moist combustion" in boiling sulphuric acid, has 
arisen, known, from the oameof its inventor, as the Kjeldahl method. 
For practical commercial purposes, such as the examination of 
manures, where accuracy in small decimal percentage places is not 
sought, both methods give substantially the same results. It is. how- 
ever, now largely conceded thai the Kjeldahl process, properly modi- 
fied, is the more trustworthy ; and, from Its cleanliness, convenience, 
and simplicity, it has in K upland and in Germany now practically 
supplanted the soda-lime method, and, I understand, has also to a 
large extent done so in America, although I believe your chemists 
still recognize the soda-lime method as an alternative official process. 
The 1893 wheat-soil samples have all been examined by both proc- 
esses, and as there is throughout a slight difference in the results, 
it is considered important that both should be recorded, for although*, 
as will presently appear, it is desirable to accept the Kjeldahl results 
as the more satisfactory, it is, on the other hand, important to pre- 
serve the soda-lime results for comparison with those of the analyses 
of the earlier series of samples, which were made by the soda-lime 
method. It is. moreover, interesting to those who are practical ami- 
cultural chemists to see the nature and range of the variations 
between the two sets of results. These are set out in Table 9. The 
nitric nitrogen is also added separately. 
