46 SOIL VENTILATION 
that it can breathe from the air the gases needed by 
the plant root. 
Tuberculosis enters our insufficiently ventilated homes 
and soil exhaustion enters upon the compact, non-porous 
soils. 
We must ventilate our homes if we live, and this is 
as applicable to the soil as it is to man. 
Soil ventilation can be secured by drainage, deep 
tillage and plowing in, of course, organic matter. Cer- 
tain plants, like the alfalfa plant, penetrate their roots 
deep into the soil and when they decay leave openings 
into which air finds its way. Next to drainage, soil 
ventilation is best secured by the plowing under of heavy 
crops of organic matter, such as corn stalks, rye, vetch, 
buckwheat, hungarian, clover, etc. 
It must not be forgotten that a soil filled with water 
cannot possibly breathe, neither can a close, compact 
soil, so a soil may be fairly well drained and yet not 
be properly ventilated; hence the need of organic matter 
to aid in soil ventilation. 
The necessity for soil ventilation is not only that 
oxygen may come in contact with the plant roots, but 
that a proper home may be established in the soil for 
the vast multitude of bacteria, so that they can perform 
their work of changing the nitrogen of decaying organic 
matter into a form suitable for plant food. 
It seems that bacteria in the soil are affected by en- 
vironment as well as man, so conditions of the soil will 
influence and modify their growth. 
Soil bacteria being essential to a good, living, work- . 
ing soil, then we can see the need of effective soil ventila- 
