THK BROADHALK WHEAT SOILS. 
89 
The foregoing digression followed on the consideration of the chlo- 
rin results, which, as dealing with water-soluble constituents, appealed 
related to the water-soluble nitrates. 
GENERAL COMPARISON OF THE QUANTITY OF TOTAL NITROGEN 
PER ACRE IN THE ROTHAMSTED SOILS AND SUBSOILS WITH 
THE QUANTITY ANNUALLY AVAILABLE OR UTILIZED WHEN 
NONE IS SUPPLIED BY MANURE. 
Plal 5 on the Broadbalk wheat field, continuously manured with 
minerals, hut receiving no manorial nitrogen, and at present in a state 
of starvation for lack of a suflieienl supply of nitrogen in an assimil- 
able form, nevertheless contains, in round numbers, in the first '27 
inches 6,401 pounds (or nearly •*) tons) of nitrogen per acre. We 
remarked t hat , notwithstanding 1 his large quantity of nitrogen, experi- 
ence teaches that a small lop-dressing of sodium n it rate or of ammo- 
nium safts would in a single season convert the DOOT yield of this plat 
from L4j bushels of wheat , w ith 1<»1 hundredweight of stunted straw 
per acre, into a rich crop of probably '■>■'> bushelsof wheat wit h a luxu- 
riant growth of straw. We observed, then, thai nature was but nig- 
gardly in her annual doles from the great store of total nitrogen 
naturally contained in her surface soils, and we asked, "What does 
she spare us, and how?" At thai point we turned aside to examine 
the question of the nitric nitrogen contents of the field as revealed 
by the Latest series of analyses, and we may now return to the former 
question. 
By the consideration of various Rothainsted results an attempt has 
been made to estimate the quantity of nitrogen annually rendered 
available by natural means for plant food on soils cither unmanured 
or manured with mineral dressings only. The plats selected for 
examination have been plats 3 and 5 of the Broadbalk held, examined 
separately and in different ways in the light of the analyses of the 
1SSJ and 1 S1K} samples; the unmanured plat (plat 3) of the grass land 
of the park, with its mixed herbage (estimate for fort}' years) ; the 
unmanured continuous root-crop plats in Barn field (estimate for 
thirty-sis years); and the unmanured plats and superphosphate plats, 
representing seven courses (twenty-eight years) of four-course crop 
rotations in Agdell field. We have also the results obtained by the 
constant analyses (over twenty years) of the waters running from the 
fallow-soil drain gauges. 
BROADBALK FIELD. 
The first results to be referred to relate to the produce of wheat 
over thirty years in Broadbalk field, firstly, on plat 3 without manure, 
and. secondly, on plat 5, with mineral manure only. 
