X. DRAINAGE AND VENTILATION 



Drainage. Professor Shaler estimated that there are more 

 than one hundred thousand square miles of swamp lands lying east 

 of the 100th meridian which are the richest and most produc- 

 tive lands in the United States. 



In this list might be mentioned the Great Dismal Swamp and 

 the Florida Everglades. In these regions nothing but swamp 

 vegetation will grow unless the lands have been drained to some 

 extent. Farm crops will not grow on them for the following 

 reasons: (1) the temperature is too low; (2) the soil ventilation 

 is inadequate. 



The advantages of good drainage cannot be overestimated. Some 

 of its benefits are as follows: 



1. It gives greater depth to the subsoil and hence gives the plant 

 more room. But few plants raised by the farmer are hardy enough 

 to force their roots into water-filled soils deprived of nearly every 

 vestige of air. 



2. Drainage warms the soil by admitting air to the soil and by 

 lessening the amount of evaporation. 



3. It increases the amount of plant food by favoring the growth 

 of germs which prepare nitrates for the use of plants from the un- 

 available nitrogen of the soil. 



4. It makes plowing possible earlier after rains and enables the 

 farmer to begin his work earlier in the spring. This lengthens the 

 growing season and produces more mature crops. 



5. It improves the texture of the soil by making it loose and 

 mellow. 



6. It increases the porosity of the soil and enables the plant's 

 roots to sink deeper into the rich and comparatively unleached 

 soil. 



7. It prevents the soil from being wasted by heavy washing 

 after rains. 



8. It fortifies plants against dry weather by enabling the roots 

 of plants to go deeply into the soil where moisture can be found. 



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