BARN FIELD ROOT-CROP soILS. 
167 
It will suffice to direct your attention specifically to the results for 
the first 9 inches OT surface soils, and the figures may be simplified 
by averaging the three plats — 4, 5, and 6 — the treatment of which has 
been somewhat similar. 
It is now well recognized that root crops grown with mineral 
manures alone perhaps exhausl the available nitrogen of the surface 
soil more than any other crops, and if we look at the results for 
plats 4, 5, and • we find that in the surface samples of the first series, 
where nothing but mineral manure is used, there is on the aver- 
age (see summary at foot of Table ss) o.iisim; per cent of nitrogen. 
Compared with those soils of the wheat or barley land on which 
mineral manures only are used, this percentage of nitrogen is 
decidedly low, while at the same time the annual yield of nitrogen in 
the root crops under the influence of mineral manure alone is 
decidedly greater than that in ihe cereal crops. 
When the same three plats have b'-cn annually supplied with 
sodium nitrate, as in series 2, we ai once Bee a very tangible increase 
in the proportion of nitrogen, there being found (see summary) on 
the average < >.< r.i;,:; per -cut of nitrogen on these plats, as against 
( i. osm; per cenl in series 1 . 
In series •'!. where a like quantity of nitrogen lias been regularly 
supplied in the form of ammonium salts, we get almost the same 
average result as with the sodium nitrate, namely, 0.0042 per cent. 
In series I and aeries 5, on which rape eake has been abundantly 
applied, there is throughout a farther increase in nitrogen, the 
average percentages in the three plats being <>.1<)4!» in series 4 and 
<» L016 in series 
We know thai neither ammonium salts nor nitrates accumulate in 
the soil, and no doubt, therefore, the increased quantity of nitrogen 
in series 1 and series 1 is due to accumulated crop residues, corre- 
sponding to the increased growth shown in the preceding table. 
On series 4 and series 5 there has also been greater growth and 
more root residue, but the increased proportion of nitrogen may be 
due not merely to this, but also to some extent to accumulation of 
manurial nitrogen derived from the rape cake. 
It will be further noticed thai on the three plats — 4, 5, and 6 — the 
proportion of nitrogen is greater in series 4, where the rape cake has 
been supplemented by ammonium salts, than in series $, where the 
rape cake has not been so supplemented, and if we refer to the pre- 
vious table, showing the average crop results, it will be seen that 
plats 4, 5, and 6 in series 4 show throughout very considerably larger 
average crops than in series 5. 
In the case of the plat which has received no mineral manure the 
effect of the varied treatment in the different series is also shown in 
the results of the soil analyses. 
