Page 31 - Ilmu Tanah

18 The Chemistry and Fertility of Soils under Tropical Weeds

6. How do multivalent cations behave with the changes in soil pH in dryland soils?
7. How do multivalent cations behave with the changes in soil pH in wetland soils?
8. How do the chemical properties of paddy soils behave in response to the changes in soil
pH and E?
9. How do the chemical properties of paddy soils behave in response to flooding and
drying?
10. Explain the effect of the changes in soil pH on the magnitude of soil CEC and base
saturation!
11. Explain the effect of the changes in the soil pH and soil E on the reactivity and mobility
of multivalent metal cations!
12. Explain the fates of free ions in soi-water system!
13. What is the importance of adsorption/desorption reactions and ion exchange in the soil
environment? Explain!
14. What is the importance of precipitation/dissolution reactions and soil mineral
weathering in the soil environment? Explain the soil pH at which these processes occur
when the concentration of metals is low or high!
15. What is the importance of adsorption/desorption reaction and ion exchange in the soil
environment?
16. What is the importance of enzymatic reaction and organic matter decomposition in the
soil environment?
17. Explain the P cycle related to the role of phosphatase! What does this enzyme exactly
do in the cycle?
18. Explain the S cycle related to the role of arylsulfatase! What does this enzymes exactly
do in the cycle?
19. Explain the N cycle related to the role of protease! What does this enzyme exactly do in
the cycle?
20. Where do the soil enzymes come from?
21. What is the importance of oxidation/reduction (redox) reactions in the soil
environment?
22. Explain the role of pH in controlling the above reactions that occur in the soil
environment!
23. What is enzyme? What is its role in the soil environment?
24. How do base cations behave in the soil environment?
25. How do acid cations behave in the soil environment?
26. How do the nutrient element anions behave in the soil environment? What happen to P
anions in response to the changes in soil pH?
27. How do weeds change the soil pH and stimulate the dissolution of soil mineral matters
and the decomposition of soil organic matters?
28. How do the secreted organic acids and enzymes participate in the processes of soil
mineral dissolution and organic matter decomposition?
29. How do the soil CEC, exchangeable base cations, and exchangeable acid cations
response to the changes in soil pH stimulated by weeds? Explain!

Abdul Kadir Salam and Nanik Sriyani – 2019