356 



SOIL PHYSICS AND MANAGEMENT 



tion must necessarily be deep, and is always accompanied by root 

 injury. In some alluvial bottom land ridging may be necessary. 

 Where the annual morning glory or other troublesome weeds are 

 thick deep cultivation may be advisable to cover them, especially 



r - 



Fio. 173. Ridged cultivation with drilled corn. A very undesirable method with nearly 



all soils. 



if the corn is drilled and not checked. This forms a very strong 

 objection to drilling corn. The ridge formed is sometimes six to 

 eight inches high. The disk cultivator 9r the little diamond plow 

 are both used for ridging. The ideal cultivation is not absolutely 

 level, but such as to have a slope of one to two inches between rows. 

 Compare figure 172 and figure 173. 



QUESTIONS 



1. What was Jethro Tull's theory of plant nutrition? 



2. Define tillage. 



3. Why is loosening the soil necessary ? 



4. Give results obtained for plowing and not plowing. 



5. What are the advantages of turning under vegetable matter? 



6. Give advantages of killing weeds. 



7. Give tillage for storing and conserving moisture. 



8. Why is compacting necessary? 



9. Give action of mold-board plow in turning soil. 



10. What conditions are necessary for best pulverization? 



11. What is the advantage of the stubble plow? 



12. What is the objection to using it in plowing sod? 



13. Describe the general purpose plow. 



14. Describe the sod plow and its work. 



