1758 



The Cornell Reading-Courses 



OxLfqen 



OxLjqen 



^^arbon dioxide 



secured by the aid of certain soil bacteria and leguminous crops, and be- 

 cause of its many beneficial physical effects on the soil. Its increase 

 is accomplished, according to circumstances, by means of large crop 

 residues to which rotation and inoculation contribute, by the use of stock 



manure, and by the 

 7he afmosphere utilization of green- 



manure crops. 



Tillage 



Tillage, deep and 

 thorough, stirs and 

 fines the soil, incor- 

 porates manures and 

 fertilizers that may be 

 added, and contributes 

 to general ventilation 

 and sanitation. 

 Various implements 

 may be employed, 

 according to the needs 

 of the soil. 



Fertilizers 



Carb 



Root h<iii;s-' 



^^^■-- 



Tubercles 



The soil atmosphere 



soil 



Water 



The chemical 

 nature of the average 

 soil is such that, by 

 the proper adjustment 

 of the conditions of 

 moisture, lime, organic 

 Diagram of a leguminous plant {clover), showing matter, and tillage, 



the largest possible 

 quantity o f plant- 

 food will be made 

 available and the soil 

 will be maintained in 

 a sanitar}^ condition. 

 Nitrogen should be suppHed through the organic matter. On many 

 soils devoted to the deep-rooted, slow-growing crops, such as fruit, 

 commercial fertilizers may not be needed. In other cases their use 

 should be reduced to such quantities and forms as will give the greatest 

 economic results. The treatments preceding the application of a fertilizer 

 should all contribute to a rise in its efficiency. 



^19- 3- . . 



its parts m relation to the soil and the atmosphere, and 



something of the circulation of the plant-food elements. 

 From the atmosphere and water the plant derives carbon, 

 hydrogen, and oxygen. From the soil it derives potassium, 

 phosphorus, sulfur, iron, calcium, and magnesium. Nitrogen 

 from the soil atmosphere is elaborated in the root tubercles by 

 certain bacteria. Products of growth are given of by the 

 leaves 



