350 On the Rain and Drainage- Waters at Rothamsted. 
drainag;e within the period of our determinations ; in this year, 
1879-80, the mean drainage was 9'808 inches, and the mean 
quantity of nitrogen as nitrates removed in the drainage-waters 
31"78 lbs. per acre. 
In a field of good natural drainage, with a soil of the same 
physical characters as our drain-gauge soils, we should expect 
the amount of drainage to be the same when both were under 
bare fallow. It, however, by no means follows that, with an 
equal production of nitrates and an equal drainage, the soil 
exposed to a one year's fallow would lose as large a quantity of 
nitrates as the soils of the drain-gauges. The average amount 
of nitrates lost by the drain-gauge in a year may perhaps fairly 
represent its annual production ; but in order to part with this 
amount it must itself contain much more, as the soil is never at 
any time thoroughly exhausted by drainage.* Unless, therefore,, 
the production of nitrates is far more active in the field than 
in the drain-gauge, the amount lost during the first year of 
fallow would be much less than that experienced at the drain- 
gauge. Again, nitrates being produced chiefly in summer time, 
an ordinary bare fallow suffers only from autumn and winter 
drainage, and not from that of the whole year. 
Though for the reasons just given the loss of nitrates by 
drainage may be considerably less in an ordinary agricultural 
fallow than in our own drain-gauge experiments, the loss must 
clearly be a very serious one whenever the season is wet. Bare 
fallow can only be thoroughly successful in a dry climate. 
Under such circumstances the active production of nitrates 
which takes place in a fallow will doubtless greatly increase 
the fertility of the soil for the succeeding crop. In a wet climate 
the practice of bare fallow must result in a rapid diminution of 
soil-nitrogen. The influence of cropping on the loss of nitrates 
by drainage will come under notice in Part III. of this paper. 
We have already, however, had illustrations of one mode in 
which a crop will greatly diminish such loss, namely, by largely- 
increasing the amount of evaporation, and thus diminishing the 
amount of drainage. 
( To he continued.^ 
* Of the large amount of nitrates contained in tlie drain-gauge soils we get 
some idea from the fact that the 20-inch gauge parted with over 02 lbs. off 
nitrogen jser acre in 1878-9, and still was far from being exhausted. 
