TILLAGE 



While the farmer depends somewhat largely on the 

 weathering agencies for granulation of his soil, maximum 

 tilth can be obtained only by certain external operations. 

 The advantages to be derived from drainage have been 

 pointed out. The importance of the addition of lime 

 and organic matter as a means of soil improvement has 

 been emphasized. Yet, after all these have been pro- 

 vided, a further fundamental practice reznains to be 

 followed. This practice is tillage, or the manipulation 

 of the soil by means of implements so that its struc- 

 tural relationships may be made better for crop growth. 

 Tillage is so general in its application, so pronounced in 

 its ejffects, and so complex in its modes of operation, and 

 has to do with so many machines employing different 

 mechanical principles, that it requires discussion by itself. 



565. Objects of tillage. — Tillage aims to accomplish 

 three primary purposes: (1) modification of the struc- 

 ture of the soil; (2) disposal of rubbish or other coarse 

 material on the surface, and the incorporation of manures 

 and fertilizers into the soil; (3) deposition of seeds and 

 plants in the soil in position for growth. 



The most prominent of these purposes is the modifi- 

 cation of the soil structure. This affects the retention 

 and movement of moisture, aeration, and the absorption 

 and retention of heat, and either promotes or retards the 



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