494 
Lifluence of Climate on Cultivation. 
expand and flourish in weak soils and assimilate prodigious 
quantities of nitrogen, which would otherwise be all but lost. 
Irrigation might no doubt cause nitrogenous manures to be 
held in greater repute in the sandy turnip-soils of the south ; 
but, in the absence of such appliances, vegetable manuring 
is found to add to the fertility of the soil when phosphoric 
and ammoniacal manures have ceased in a great measure to 
add materially to the growth of the crop. 
Accordingly, phosphoric manures are most advantageously 
applied to late sown crops of turnips, whose period of growth is 
comparatively short. Those varieties, on the other hand, which 
are sown earlier, or where the soil or climate tends to promote 
their extended healthy growth, admit of larger quantities of 
nitrogenous manures being applied. It is often a matter of 
indifference whether late-sown turnips be dressed with guano or 
superphosphate of lime. By the aid of a ready supply of phos- 
phates, they find as much ammonia in the soil and atmosphere 
as they can assimilate, and consequently none need be added. 
Where the climate and state of the soil admit of early sow- 
ing, nitrogenous manures are indispensably necessary to pro- 
duce full crops. Large quantities of Peruvian guano are 
applied to Swedes with the best results on the deep and rich 
loams of the Lothians. Early sowing counteracts any ten- 
dency which the plants may have to produce an undue amount 
of leaf. On the other hand, on light soils, where the five- 
course rotation is followed, in which the land lies two years 
in pasture, phosphoric manures are relatively more valuable ; 
the later varieties of turnips are generally sown, and the physical 
properties of the soil do not admit of the largest crops being 
grown. In these circumstances it is found that superphosphate 
is as valuable a fertiliser as the best guano : this only holds, 
however^ on dry soils. On the other hand, guano produces 
larger crops on undrained land or on the more retentive class of 
soils. In the latter cases, the soil possesses superior mecha- 
nical properties, which alone can permit the plant to arrive at 
the full development of its capacities of gx'owth. 
In the cultivation of the turnip-crop, in climates and soils of 
different natures, the same principles may be otherwise illustrated. 
Where the soil and climate are only suited to grow small-sized 
roots, the crops are sown on the flat and drilled at narrow intervals. 
For the same reason, the sowing of turnips broadcast is still fol- 
lowed in some instances, on inferior descriptions of soil, in 
the eastern counties. As the soil and climate become more 
suited to grow larger roots and larger crops the spaces assigned 
to the individual plants become greater. In the light soils 
of the south, where phosphoric manures alone are almost suf- 
