On the Rain and Drainage - Waters at Rothamsted. 
39 
quently the drainage, even in summer time, always contains 
a large amount of nitrates. Intermediate between the two 
descriptions of manuring just mentioned stands Plot 11, which 
receives superphosphate, but no potassium-salts ; here more 
nitrogen is taken up by the crop than on Plot 10, and less appears 
in the drainage-water ; but the assimilating power of the crop 
being limited bv the scarcity of potash its action does not 
nearly equal that of the crop on Plots 7 or 13. Plots 12 and 14, 
receiving respectively sulphate of sodium and sulphate of mag- 
nesium, together with the superphosphate, and having some 
residue of potash from early applications, stand intermediate 
between Plots 11 and 13 as to the proportion of nitrates assimi- 
lated by the crop, and consequently diverted from the drainage- 
water. An examination of the drainage from the various plots 
in summer time thus affords an excellent indication of the relative 
rate of assimilation of nitrogen taking place in the crops of the 
different plots. 
In autumn the drainage-waters still reflect the results produced 
by the crop during summer. Where the crop has left a con- 
siderable residue of nitrates unassimilated, there the drainage- 
waters contain nitrates in considerable quantity, but where the 
crop has appropriated the nitrates in the soil there only small 
quantities are to be found in the drainage. During winter the 
waters equalise much in composition. If drainage is at all 
considerable, the soils which at the end of summer were richest 
in nitrates gradually lose their excess, while fresh nitrification 
maintains, or increases, the amount of nitrates in the soils 
which contained a smaller quantity. 
On Plot 8 a larger quantity of ammonium-salt is applied than 
on any other plot in the field. There is here at all times an 
excess of nitrogen over the requirements of the crop ; nitrates 
are thus found in the drainage-water throughout the summer, 
and they are maintained both in autumn and winter at a com- 
paratively high figure. 
The effect of the nitrate of sodium on Plot 9 will be best noticed 
in this place, as, like the ammonium-salts on the plots just con- 
sidered, it is applied to the land in the spring. The quantity 
of nitrogen supplied in the nitrate of sodium is very nearly 
identical with that supplied in the form of ammonia to Plots 
7, 10, 11, 12, 13, 14 and 15. As the whole of the nitrogen is 
already in the form of nitrate when applied to the land, the first 
drainage-waters from this plot are naturally much richer in 
nitrates than where ammonium-salts have been employed, for 
in the latter case a gradual process of nitrification must be 
gone through before the nitrogen can appear in the drainage. 
The mean of five April runnings from Plot 9 gives 52*2 of 
