CHAPTER I. 

 THE SOIL. 



By PROF. A. R. WHITSON, 

 Department of Soils, University of Wisconsin. 



SECTION II. RELATION OF THE SOIL TO PLANT 

 GROWTH. 



As agriculture depends on the soil, a full knowledge 

 of the soil and its management is necessary to scientific 

 farming. The soil is an extremely complex mixture 

 with complex physical, chemical, and biological prop- 

 erties, all of which it would be interesting to study, 

 but from the standpoint of practical agriculture we are 

 interested only in those properties of the soil which 

 influence the growth of crops. We must, therefore, 

 look at the soil through the plant. 



Absorption of Water. The first effect of the soil 

 on the plant is its relation to the germination of seed. 

 This process begins with the absorption of water, and 

 the rate at which absorption takes place is influenced 

 by several factors. Firming the soil brings the seed 

 in closer contact and so hastens the absorption of water. 

 Warm water is absorbed more quickly than cold, and 

 for this reason especially, seed germinate more quickly 

 in warm than in cold soils.* 



Oxygen. Besides moisture, germinating seed re- 

 quire oxygen, so that while the soil must have sufficient 

 moisture and be in sufficiently close contact with the 



* This influence of temperature can readily be shown by placing 

 equal weights of dry peas or beans in two vessels of water, one of 

 which is warm and the other cold, allowing them to stand half an 

 hour and then drying the surface with a cloth and weighing. 



