Page 123 - Ilmu Tanah

110 The Chemistry and Fertility of Soils under Tropical Weeds

Key Questions

1. What is nutrient cycle? Explain it with an example! What is its urgence for the
sustainability of soil environment?
2. Explain the C-cycle and its role in the soil environment! How does this cycle apply to
the management of waste and agriculture?
3. Explain the N-cycle and is role in the soil environment! How does this cycle apply to the
management of waste and agriculture?
4. Explain the P-cycle and its role in the soil environment! How does this cycle apply to
the management of waste and agriculture?
5. Explain the S-cycle and its role in the soil environment! How does this cycle apply to
the management of waste and agriculture?
6. Explain the producers, consumers, and decomposers in the nutrient cycle! Explain how
to manage these components efficiently and effectively!
7. What is the role of enzymes in the nutrient cycles? What happen if enzymes are absent
in the soil environment?
8. Explain the various producers of enzymes in the soil system! How to increase the
production of enzymes in soils?
9. What is phosphatase? How does this soil enzyme work on decomposing soil organIc P
and releasing inorganic P?
10. What is arylsulfatase? How does this soil enzyme work on decomposing soil organIc S
and releasing inorganic S?
11. What is protease? How does this soil enzyme work on decomposing soil organIc N and
releasing inorganic N?
12. What is Rhizobium sp? What is the role of this microorganism in the soil system? How
does this microorganism relate to the nutrient cycles?
13. Explain the two mechanisms of C increase in soils caused by the presence of weeds!
Which one is more dominant?
14. Explain the role of microorganisms in nutrient cycles in the soil environment! Give
example!
15. What is ammonification? Explain it with the related chemical reaction! Why this
reaction is so important in the soil system?
16. What is nitrification? Explain it with the related chemical reaction! Why this reaction is
so important in the soil system?
17. Nitrification is not always good in the soil system. Explain!
18. What is urease? What is its important role in the soil environment? Why its presence in
agriculture is unwanted?
19. Why must ureases in agricultural lands be inhibited?
20. What is the role of urease inhibitors? Give examples!
21. Why is nitrate not effective if given into in flooded soils like paddy fields?

Abdul Kadir Salam and Nanik Sriyani – 2019