296 
Supplement to the " Tropical Agnculturist." 
[Oct. I, 1900. 
this result may be accomplished by simple means 
(water furrows), the process in questijii has the 
disadvantage of producing unequal heating of two 
oppositely inclined surfaces, resulting in unequal 
growth of the plants on the two sides. For this 
reason bed culture is not suited to fields that are 
to be planted with only one kind of crop. In 
such cases level cultivation which securesa higher 
and more uniform temperature is decidedly pre- 
ferable. 
If, however, this method is followed the bed 
should run north and south if the field permits 
since the difference in temperature between the 
east and west slopes is far less marked than that 
of slopes facing north and south. In other 
words, the disadvantages of unequal heating is 
least with beds running north and south, an excel- 
lent means of raising the temperature of the *oil 
in the cultivation of plants in ridges or in hills. 
Soils so cultivated have a higher average tempera- 
ture during the growing season than those culti- 
vated level. The effect is of longer duration in 
ridge culture than in hill culture, because in the 
former the ridges are constructed before seed time, 
while in the latter the hills are made in the more 
advanced stages of growth of plants. For this 
reason ridge culture is especially suited to plants 
which require a considerable amount of heat 
(maize, sunflower, beets, &c„) in climates un- 
favourable, as regards temperature, to the growth 
of these plants. However, this is true only for 
regions in which the weather in spring is not too 
cold, for the plants growing on the top of the 
ridges are, on account of their exposed position, 
more easily injured by late frosts in spring than 
those planted on the level soil and hilled up later. 
As a general rule, both these methods are mainly 
adopted to such soils as have little capacity for 
collecting and retaining heat (clayey and calcare- 
ous soil), and which are also apt to collect excessive 
quantities of water. It is evident that the increase 
of temperature due to ridge or hill culture is of 
no advantage on soils of little water capacity and 
great permeability (savid) when precipitation is 
scanty. Under sush conditions level culture is to 
be preferred. It should be remembered when 
ridge or hill culture is used that ridges running 
north and south are of higher and more uniform 
temperature than those running east and west. 
Regulation of the store of water is the soil is 
another means of modifying the temperature. If 
the soil is wet elevation of temperature is brought 
about by removal of the exces/' '<i moisture. 
The proper means to this end are direct removal 
of water, lowering water capacity, and increasing 
permeability of the soil as already explained. 
That the desired result may he obtained by these 
means has been proved by various experiments. 
Another means of changing conditions of tem- 
perature in soils is intermixture with soils of 
opposite properties as regards heat. Admixture of 
sand with clay or earth rich in clay and lime- 
stone results under natural conditions in an 
average increase in the temperature of the soil, 
while the opposite process produces a lowering 
of the temprature of the soil. By thoroughly 
intermixing sand and humus a soil results 
which collects heat more rapidly and to a greater 
depth than is done by either separately. Increase 
of humus in mineral soils as, for instance, by the 
liberal application of manures of organic origin 
prevents extremes of temperature. 
