222 THE FIRST BOOK OF FARMING 



continuous cultivation of this crop tends to exhaust 

 the supply of organic matter in the soil. 



How does cotton growing affect soil texture? 



Cotton growing wastes soil humus and therefore 

 injures soil texture by making the lighter soils more 

 loose and open, and the heavier soils more dense 

 and compact. 



How does cotton growing affect soil water? 



By wasting humus cotton growing injures soil 

 texture and so weakens the water holding and water 

 pumping power of light soils and weakens the water 

 absorbing power of heavy soils. Therefore the con- 

 tinuous cultivation of cotton weakens the power of 

 the soil over water, that most important factor in 

 crop growth. 



How does cotton growing affect soil ventilation? 



Continuous cotton culture, by wasting humus, in- 

 jures texture and therefore injures soil ventilation, 

 causing too much ventilation in the lighter soils 

 and too little in heavier soils. 



How does cotton culture affect plant food in the 

 soil? 



Continuous cotton growing wastes plant food: 



Because it wastes organic matter which contains 

 valuable plant food, particularly nitrogen. 



Because by wasting organic matter it increases 

 the leaching of the lighter soils and the surface 

 washing of the heavier soils. 



Because its roots occupy largely the upper soil and 

 do not make use of much food from the lower soil. 



Because it grows only during the warm part of 



