CHAPTER XXVI 



TILLAGE 



IN the time of Jethro Tull (1GT4-1741) the present theory of 

 plant nutrition liad not been advanced, and this well-known hus- 

 bandman frequently made the .statement that "tillage is manure." 

 While his theory was wrong, yet his practice was right. He believed 

 that the object of fining the soil was to enable the plant to take up 

 the small particles for growth. The practice resulting from this 

 belief was as good as would have been brought about had the real 

 theory of plant nutrition been known. We know now that the pur- 

 pose of tillage is not to furnish fine particles of soil for the plant. 

 However, tillage accomplishes a number of objects, many of which 

 are closely related to the production of plant food for the crop. 



Tillage is the practice of working the soil for the purpose of 

 bringing about more favorable conditions for germination and plant 

 growth. All operations that affect the soil by stirring, inverting, 

 fining, or firming are included in tillage. The most common are 

 plowing, harrowing, rolling, and cultivating. 



THE OIWECTS OF TILLAGE 



1. Pulverizing and Loosening the Soil. The natural ten- 

 dency of soils is to become compact, principally through the action 

 of rain, and in spite of the influence of the roots of plants and the 

 organisms in the soil whose tendency is to keep the soil loose and in 

 good tilth. It is necessary, then, to stir the soil to allow the funda- 

 mental processes that are vital to crops to take place. On the brown 

 silt loam of the corn belt a rotation of corn, corn, oats, and clover 

 was practiced. The soil was plowed preceding the oat crop and at 

 no other time. The two crops of corn were planted in the unplowed 

 soil, and a yield of .'J5.' bushels per acre was produced as a nine- 

 year average. The plowed land produced l.'i.T bushels more. 1 



2. Turning under vegetable matter and incorporating it and 

 other fertilizers with the soil. In our farm practice it is necessary 

 to maintain the supply of organic matter, and this can l>e done only 

 by incorporating large quantities of vegetable material in the soil. 

 When plants die and fall to the surface of the ground, unless some 



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