FACTORS IN CROP-ADAPTATION 499 



The range of conditions upon which a particular crop 

 will grow is limited. It is wider for some crops than 

 for others. Likewise, the range of crops which can be 

 grown on any particular soil is also limited. The more 

 extreme the soil condition, the more limited is this 

 range of crop-adaptation. It is the soil of intermediate 

 properties texture, organic content, drainage and 

 food supply which is adapted to the greatest variety 

 of crops. In the largest utilization of any particular 

 soil, this adaptation of crop to soil must be made use of, 

 as well as modification of the soil. 



353. Factors in crop-adaptation. The determining 

 factors in crop-adaptation are of two sorts: (1) The 

 physiological requirements of the plant. (2) The ca- 

 pacity of a given soil and climatic condition to fulfil 

 those physiological requirements. 



354. Physiological requirements of the plant. The 

 physiological requirements of the plant are of both a 

 physical and a chemical character. 



(1) The physical requirements relate to the habits 

 of growth of the plant, particularly the type of its root 

 system and the intensity of sunshine, temperature and 

 wind it is able to withstand. Especially important is 

 the root system. Deep- or tap-rooted plants have a very 

 different feeding ground from shallow-, fibrous-rooted 

 plants. 



(2) The chemical requirements relate to food ele- 

 ments necessary to growth, and especially to the presence 

 or absence of accessory substances which the plant is 

 able to withstand. For example, some plants will not 

 grow in a soil rich in lime; others require this condition. 



