94 
INVESTIGATIONS ON EOTHAMSTED SOILS. 
CONTINUOUS WHEAT GROWING IN RELATION TO ECONOMY OF 
NITROGEN. 
Altogether, the study of the nitrogen results indicates that continuous 
wheat growing is, from a natural point of view, an extravagant mode 
of farming, only justifiable, like other extravagances, under the 
pressure of a more or less artificial environment. For the wheat crop 
has completed its growth and is harvested long before nitrification 
has ceased in the soil, and there is no crop to take up either the 
balance of the nitrates left unused by the wheat or the larger balance 
formed after the active growth of the wheat is over; and these 
nitrates must pass away in subsoil drainage during the winter, except 
where the rainfall is small, or in those latitudes exposed to long 
winter frosts. This drainage, even on unmanured land, involves a 
serious loss of nitrogen, and a still greater loss when the yield of the 
crops is artificially increased by the use of nitrogenous manure. 
Ordinary rotation farming tends, far more than continuous wheat 
growing, to conserve the natural nitrogen of the soil, and is the 
sounder method of farming where local circumstances create and 
maintain a demand for other produce than grain — as, for instance, in 
any country that is fairly closely populated. But even rotation 
farming, with its fallows, involves a waste of nitrogen owing to its 
fallow intervals, except in intensive farming, where catch crops, like 
Trifolium or vetches, can be grown — crops which absorb the nitrates 
of the soil and also add, as we know, to the stock of soil nitrogen. 
But in continuous wheat growing this can not be done. If winter 
wheat is sown, there is but a short interval between harvest and seed- 
time in which to clean the land and prepare a seed bed. It is only 
where spring wheat is grown that a fallow crop becomes possible with- 
out loss of a season; and in wheat culture on a large scale it would 
often be a question even then between the relative economy of 
conserving nitrogen or utilizing the fallow time for the destruction 
of weeds. It is, of course, in any case, only in mild and genial 
latitudes with a favorable rainfall that autumn catch crops can 
be satisfactorily raised. If circumstances allow them to grow well 
and luxuriantly, they will often smother weeds and extirpate them 
as effectually as will more direct cleansing operations; but a poor, 
thin catch crop will often only encourage the growth of weeds. 
In any ease, however, in continuous wheat growing without rota- 
t ions involving Leguminous crops, we must annually lose some nitrogen, 
and if w e are to increase, or even to maintain, the fertility of the land, 
we must sooner or later buy nitrogen, eit her directly or indirectly, in 
the market; and, il may be added, we must .waste a good deal of it. 
But we have seen that the capital of soil nit rogen is very large, and 
that it is doled out to us so slowly and sparingly that, on originally 
good and fori lie Land, it lasts a long time, despite its annual diminu- 
