FACTORS DETERMINING FERTILITY 



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FIG. 30. A fertile soil This soil possesses all the qualities, properties and conditions 

 which impart to it productive power. 



FIG. 31. Harvesting hemp in Wisconsin. Crop growth is the indicator of soil fertility 

 This particular soil is in a high state of fertility. 



Positive factors: (1) A suitable moisture supply in the soil. 

 (2) Sufficient air in the soil. (3) Good tilth (Chapter V). (4) 

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