132 SOME PRACTICAL LESSONS FROM SOIL BACTERIOLOGY 
drawn the practical lesson that a properly kept farm should keep 
plenty of live stock and, instead of selling its manure, should use 
it freely on the soil. 
FALLOWING 
It is an old idea that the soil, after yielding several crops, needs 
a rest, an idea that goes back as far as the Romans. From this 
arose the plan of occasionally allowing the soil to remain without 
a crop for a season or for part of a season. ‘This plan has prac- 
tically gone out of use in all ordinary soils, for careful study 
shows that a detriment rather than a benefit results from such 
fallowing. Under certain conditions fallowing is an advantage. 
There is a smaller loss of water from fallow land than from land 
with growing crops, due partly to the increased evaporation from 
the stirred soil and partly to the fact that crops draw quantities 
of water from the soil, to be evaporated from the growing leaves. 
In climates where water is scarce and must be conserved, fallow- 
ing results in advantage. It is also claimed that fallowing may 
enable the soil to dispose of the poisonous secretion from plants 
that would injure a second crop growing on the same soil. But, 
apart from these facts, fallowing results in a loss to the soil. In 
the first place, fallowing adds nothing to the soil, while a crop, 
especially a legume, may do so. Moreover, during the fallow 
season the bacterial activities in the soil continue, converting the 
material in the humus into nitrates and other soluble substances, 
which are then available plant foods. Ifa crop is growing in the 
soil these will be absorbed by the crop and utilized. If, however, 
the land is fallow, there is nothing to utilize these products as 
they are formed, and they will be, in a measure, lost; for they will 
be dissolved in the soil waters and drained away from the soil 
into the general system of brooks and streams. If, in the mean- 
time, nothing of any value is added to the soil, at the end of the 
fallowing it will actually be poorer than at the beginning, except 
in the matter of water. Its store of humus will be partly converted 
