THE BROADBALK WHEAT SOILS. 
91 
estimate of nitrogen removed in the pipe drainage the actual quan- 
tity of nitrogen found unused in the autumn to the depth in two eases 
of '27 inches and in one case of 9<> inches. From t liese latter est i mates 
w e find for plat 8 3 and 5, 35. i' 1 1 DOU nds and 34.42 pounds per acre, respec- 
tively, of nitric nitrogen contained in the lirst 27 indies. But if on 
plat .") we include the nitrates found in the lower depths, we get about 
♦J pounds more, viz, 40.47 pounds per acre per annum. 
No allowance is made for the nitric nitrogen temporarily stored as 
roots, stubble, and weed residue, which for the moment are regarded 
as part of t he soil. 
GRASS LAND. 
Next we have the result s calculated from observations made on the 
grass land of the park with its mixed herbage, the plat taken for 
examination being the unniannred plat, plat 3. These results are 
given in the following short table: 
T.vi'.i.i. r.». Th* park, Kotfatinst<d— Grass land (mixed hrrbage) 1 }>I<tt 3 
I numanured >. 
Pounds 
per acre. 
Nitrogen contained in OTOps . first twenty years (lS5f>-75). first 
crops only 33. 
Nitrogen derived from rain, dew, eta | estimated) 5.<» 
Difference 28. 
Nitrogen contained in crops, second twenty vears I 1st crops 36.0 
(1876-95) )9d crops ... 13.2 
Total 39.2 
Deduct nitrogen derived from rain, dew. etc 5.0 
Difference __ 34.2 
Dnring the first twenty years, in which the first crops only were 
removed from the land, the annual removal of nitrogen in hay was 
13 pounds per acre; of this o pounds annually is estimated to have 
been supplied by rain, etc., leaving 28 pounds removed in the crops. 
During the second twenty years, 1S7U-1S05, both the first and sec- 
ond cuttings were converted into ha\ and removed, involving a total 
removal of nitrogen of :>".). l' pounds per annum — leaving, after deduct- 
ing the 5 pounds supplied by rainfall, a removal of pounds of 
soil nitrogen. 
It is to be borne in mind that tin 4 mixed herbage contains a certain 
proportion of leguminous vegetation, and that, in virtue of the pres- 
ence of this, some amount of fixation of free nitrogen would contin- 
uously go on, which would reduce to some extent the quantities 
otherwise assumed as derived from the soil itself. 
