LAKD DRAINAGE 



CHAPTER I 

 CHARACTERISTICS OF SOILS 



NEXT to the soil itself, water is the most important 

 factor in crop production. Without it, crops cannot be 

 grown. Its abundance is desirable, but its control is 

 more important than its abundance. Its control is impor- 

 tant not only because of the immediate functions of the 

 water, but because also of the degree to which its presence 

 or absence may affect other factors essential in crop pro- 

 duction. A brief study of these relations is essential to 

 an understanding of the subject before us. 



1. Chemical and physical composition of soils. A 

 soil of good chemical composition is one in which all of 

 the food elements which crops obtain directly from the 

 soil are found in abundance. 



A soil of good physical composition is one in which 

 organic matter (chiefly vegetable materials) and the 

 various kinds of mineral matter sands, silt, and clay 

 exist in desirable proportions. 



A soil lacking in chemical and physical composition 

 cannot normally produce a good crop. On the other hand, 

 it does not follow .that fit chemical and physical compo- 

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