Agrarian Zone 



The portion of a country that can be cultivated. 



Agrestal 



Refers to an organism that grows in arable ground. 



Agrology 



The study of soils. See Edaphology. 



Agronomy 



The study of the production, processing, and use of farm 

 crops. 



Agrophilous 



Refers to organisms that grow well in grain fields or other 

 areas resulting from man's activities. 



Agrostology 



The branch of systematic botany dealing with grasses. 



A Horizon (Soil) 



The stratum of soil consisting of one or more of the 

 following layers. (A horizon, partly decomposed or matted 

 plant remains lying on top of the mineral soil. A 00 horizon, 

 the relatively fresh leaves and other plant debris, generally 

 of the past year, lying on the A horizon.) AI horizon, the 

 surface mineral layer, relatively high in organic matter, 

 usually dark in color. A 2 horizon, below the A x horizon, in 

 places the surface layer, usually lighter in color than the 

 underlying horizon, in which leaching of solutes and sus- 

 pended materials occurs. A 3 horizon, transitional to the B 

 horizon, more like A than B, sometimes absent. 



Aiphyllus 



Evergreen. 



Air layering 



A method for producing roots on a stem in an aerial 

 position. 



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