292 
Swppltment to the "Tropical Agriculturist." [Oct. 1, 1901. 
Soil aeration is an absolute necessity if heavy 
and healthy crops are to be obtained by culti- 
vation. To aerate the soil we must till it, and 
this soil turning by various methods lies at 
the bottom of all improvement. 
In fact, ceteris paribus, the better aerated 
the soil the more fruitful will it be. ' ' Air-feed- 
ing " of soils is thus of the utmost importance 
to them and the crops they bear. The Fruit 
Grower is very strong on the subject of drain- 
ape. " We are so freely convinced of the value 
of drainage," it says, " that we have said that 
all soils for fruit-culture cannot be drained too 
freely — and we repeat it— whether the land be light 
or heavy." The object to be sought in drainage 
is to ensure the disappearance of water through 
and down into the soil. The important results 
of such drainage (and especially under-drainage) 
are the increased mechanical action and air 
absorption that follow. When a soil is well 
drained the rain percolates through it readily 
and sinks tolerably fast into the soil below- 
Then, it must be remembered that air pressure 
exerts a force equal to 15 lbs. sq. in. As a 
result, when rain passes down air is forced to 
follow, and thus it is that the well-drained soil 
is aerated by a natural process. The air is, 
therefore, both drawn and forced into the soil, 
and the more freely this mechanical process is per- 
formed, the better for the fertility of the land. 
In badly-drained land, on the other hand, 
the rain instead of sinking down into the 
earth is carried away, and thus soil seration is 
prevented, and the fertility brought from the 
air by the rain lost. Though the air collects 
small proportions of fertility from the air, what 
it does bring is valuable, and the more that 
can be obtained in this way the better. The 
rain brings down from the air carbonic acid 
gas, ammonia salts and Laceognitric acid, and 
that is why plants look so much fresher after a 
shower in dry weather than they did before. 
