38 CHEMICAL COMPOSITION OF SOILS 



QUESTIONS 



1. How may the chemical composition of soils be expressed? Distinguish 



between element and oxide. 



2. Name the more important elements of which soils are composed. Give 



symbol for each. (See table.) 



3. In what form do the elements occur in soils? 



4. Name four of the soil elements with which you are more or less familiar. 



5. Describe the elements calcium, magnesium, sodium, potassium 



and phosphorus. 



6. Which is the most common and abundant element on the earth? In 



the universe? 



7. Name the common mineral elements contained in soils. 



8. Name the essential elements which crops take from soils. 



9. Which elements are most commonly deficient in soils and which affect 



crop yields the most? 



10. Name the elements commonly regarded as the fertilizing elements. 



11. What can you say concerning the amount of the four most important 



elements in soils? 



12. How is nitrogen held in soils? 



13. Of what importance is decay in plant growth? 



14. What is meant by lime? 



15. Distinguish between potassium and the common meaning of "potash." 



Between phosphorus and "phosphoric acid." 



16. What is potash? 



17. In what two ways are soils of use to plants? 



18. How does the chemical composition of plants compare with that of soils? 



What are ashes? 



19. Name all the elements required in plant growth. What are the sources 



of these elements? 



20. Do plants take hi nitrogen through their leaves? How then do they get 



this element? 



21. How do plants get their carbon? 



22. What per cent of a corn kernel is carbon? Of clover hay? 



23. How does the chemical composition of an animal body compare with that 



of plants and the soil? 



24. What is a great work of plants? 



25. What is the business of the farmer? 



26. Compare the amount of wood fuel or coal burned in a stove in your home 



with the amount of ashes removed. Explain. 



27. For summary of Chapter III in outline form see table of contents. 



