PREPARING THE SEEDBED 89 



down between trench plowing and subsoiling. Trench 

 plowing is the turning of the bottom of the furrow up 

 on top of the seedbed. This is usually done by a pecu- 

 liarly constructed plow following in the furrow of the 

 breaking plow. 



Subsoiling is the breaking or loosening up of the 

 subsoil without bringing any soil to the surface. This 

 is usually done by a subsoil plow following the furrow 

 of the breaking plow and simply "rooting," or stirring 

 up the subsoil. In the heavier soil it is an advantage. 

 The plate in the bottom of the furrow where the plow 

 pressed and the horses walked year after year, is 

 broken, capillarity re-established and the roots per- 

 mitted to penetrate the subsoil. The difficulty is the 

 cost of the operation. Even though it be done only 

 once in three or four years, the returns are not enough 

 larger to justify the outlay on corn soils. 



It was found that leguminous crops, such as 

 clover, cowpeas and soy beans, rooted deep in the sub- 

 soil. The roots dying and decaying in the soil, allow 

 the air to circulate, permit the action of frost, and in 

 fact act as a complete and successful subsoiler. There- 

 fore, owing to the value of these crops as soil fertilizers 

 and as foods, they have come into general use as 

 subsoilers. 



Plowing under stalks, straw or manure crops has 

 come to be necessary to the successful culture of corn. 

 In the days of the first cultivation of prairie and other 

 rich soils, the fertility was abundant. Humus was 

 plentiful and it was not necessary to look to the con- 

 servation of soil fertility or to the mechanical texture 

 of the soil. As a result of these conditions stalks were 

 burned, and corn grown year after year on the same 

 fields, as the most profitable rotation of crops. This 

 condition does not exist now. Soils that were thought 

 to be inexhaustible in fertility produce less and less. 



