On the Rain and Drainage- Waters at Rothamsted. 
65 
equalled that recovered in the increase of crop, whilst in un- 
favourable conditions it considerably exceeded it. Further, 
there can be no doubt that the actual loss b_v drainage was 
greater than the reckonings showed. These results are of very 
great importance as illustrations of the loss which may occur 
under known conditions. 
The average conditions of practical agriculture are, however, 
not such as to lead to the loss by drainage of so large a propor- 
tion of the nitrogen supplied by manure. When ammoniacal 
manure or nitrate is used, it will generally be in less quantities 
than in the experimental wheat-field, in which so much loss by 
drainage has taken place : and such manures should onlv be 
applied when there is a growing crop ready to utilise them. But 
by far the greater part of the nitrogen supplied to the soil in 
ordinary agriculture is in farmyard-manure, or is directly 
deposited by animals. In either case a comparatively small 
proportion of the nitrogen becomes immediately soluble within 
the soil, and there will, therefore, be the less liability to loss by 
drainage. If the soil be heavily manured, and rich in organic 
matter, and especially if it be water-logged, and not freely 
aerated, there will be more danger of loss by the evolution of free 
nitrogen. Further, a considerable amount of the nitrogen of farm- 
yard-manure will be ineffective, because it remains insoluble, 
and, so to speak, dormant within the soil. Again, in ordinary 
agriculture, a great variety of plants is grown in alternation one 
with another. The ground is thus covered with vegetation for 
longer, and at different, periods of the year, than in the case of 
a continuous cereal crop ; whilst the various plants will have 
various root-ranges and habits of growth. Hence the nitrates 
brought into solution are in a much greater degree arrested by 
the growing crops. It has been shown in the case of the two 
wet seasons, the full details respecting which have been given, that 
during the autumn and winter, when there was no crop on the 
ground, there was even from the plots receiving no nitrogen in 
manure, a loss by drainage of from 15 to 20 lbs. of nitrogen 
per acre per annum ; whilst from the plots highly manured with 
ammonium-salts or nitrate, the losses during the same period 
were very much greater. How great mav be the loss by 
drainage with a bare fallow in wet seasons has been fully 
illustrated by the results relating to the drainage collected from 
the soil-drain-gauges, and the fact is here again striking! v 
brought to view. 
VOL. xvin. — s. s. 
