Influence of Climate on Cultivation. 
165 
during the growing season ; more especially during periods of 
moist weatlier, when the plant is in circumstances to turn it to 
the most advantage. It is not in dry seasons, when the soil is 
least liable to suffer from being washed by rains, that these soluble 
substances are most efficacious ; but in wet seasons, when the 
real waste from such a cause should be greatest. Mr. Read with 
his usual practical sagacity justly remarks : — " Holkham is not the 
natural soil for wlicat. In those wet seasons when there w<as so 
poor a v/heat crop throughout the kingdom, the nitrate of soda 
produced the greatest results The nitrate of soda and salt 
are best applied in two dressings : the first when the wheat takes 
its earl}- start in February or March, the rest sometime in April, 
when the wheat is growing vigorously." 
The molster the climate, the more "natural" do light sandy 
soils become for the growth of wheat. The less necessary also is 
vegetable substance, as a means of sustaining growth. The 
plants in all cases feed on the same substances ; but they are only 
yielded slowly up when applied in the vegetable form, which in 
some measure supplies the plants with a daily portion of food. 
This we can easily imagine is consistent with the most eco- 
nomical application of manuring substances. A large supply of 
nitrogenous substances existing in the soil in a fit state to be 
taken up by plants, can only be economically worked up when 
they have a due supply of moisture. 
In moist seasons the English practice of sowing wheat after 
seeds no doubt aggravates their effects on the crop. Tlie straw is 
more liable to become diseased than when it is sown after root 
crops. Under other circumstances this is still more strongly 
marked in practice. Indeed all our Scotch and Englis'i notions 
respecting the qualities of soil best fitted for the wheat plant are 
in a great measure set aside in North America, where the climate 
is entirely different. Tliere the winter is so cold that the plant is 
completely checked in its growth until the summer bursts in at 
once. This season sets in hot as well as moist, and soils of light 
texture can sustain the growtli of the wheat plant. Sandy soils 
thus become in the eyes of the American farmers quite " natural" 
for wljeat. On the other hand, those which contain vegetable 
matter in large proportions are wholly unfitted for the growth of 
Avheat, as it becomes too luxuriant and liable to disease. 
It has been already stated that, in the presence of sufficient 
moisture, a higher temperature will go far to compensate for a 
smaller Cjuantity of manure. The reverse is likewise true ; a de- 
ficiency of heat is, to a certain extent, made up by a larger su])ply 
of manure. 
It ought also to be observed that manure and temperature have 
somewhat similar effects on the flowering of plants. A deficiency 
