SUB-SOILIKG, TRENCH PLOWIi^G, TILLAGE. 51 



(3) To destroy weeds and foreign plants, whicli rob 

 the crop of food and check its growth. 



Let us add that, by opening the soil, and rendering it 

 permeable to air and water, the inert materials contained 

 m it, both organic and inorganic, are convertible into 

 soluble plant food. And m regard to many of the insects 

 which prey upon our crops, especially such as work 

 beneath the soil at the roots of plants, frequent tillage is 

 found to disturb them and bring them to the surface 

 where they get picked up by birds. 



Tillage operations include all soil operations which 

 apply directly to the cultivation of farm crops — plow^ing, 

 cultivating, harrowing, and rolling, or whatever else is 

 done to bring land to a proper state to receive the seed. 

 They also include the operations of hoeing and weeding 

 the ground after it is planted. 



Plowing. — In plowing we break up the ground into 

 furrow slices, turning them over in such a manner that a 

 new surface is presented to the atmosphere. This or some 

 other mode of loosening and turning up the under parts 

 of soils is necessary to fit them for the reception of the 

 seed and the growth of crops. 



The object of plowing being to expose the upturned 

 soil to the atmosphere and to create the greatest quantity 

 of mould the furrow-slices can produce, it follows that 

 the furrow -slice which shows the greatest surface will 

 answer these ends most effectually. In the case of a 

 square cut furrow-slice this is found to result when it is 

 laid at an angle of forty-five degrees; and to this end 

 its width must be to its depth as about ten to seven. 

 If the furrow-slices are ragged, open, and broken, and 

 if, being cut of vai-ious depths and widths, they are laid 

 at different heights, the work is inferior. A uniform 

 depth of tilth cannot then be provided by the harrow, 

 and the seed will be unequally buried. 



