Page 47 - Ilmu Tanah

34 The Chemistry and Fertility of Soils under Tropical Weeds

13. Explain the weathering of soil primary minerals! Why is it so important for the soil
chemical and fertility?
14. Explain the decomposition of soil organic matter? Why is it so important for the fertility
of soils? Which nutrients released through this soil chemical process?
15. Explain all forms of nutrient elements in the soil environment! Explain how they relate
one to another!
16. Explain the easiness of each nutrient element forms to be absorbed by weed roots!
17. Which forms of the soil nutrient elements in the soil environment readily available to
weeds? How are these forms balanced when their concentrations in the soil water are
somehow depleted?
18. Which forms of the soil nutrient elements in the soil environment are slowly available
to weeds? How do these forms relate to the weed root absorption?
19. Explain the nutrient element complexes, complexation, and complexation constant!
20. Explain the chelation, chelates, and dechelation of nutrient elements!
21. Explain the relationship between all the mechanisms controlling the free ions of
nutrient elements!
22. Compare the concentrations of free ions, total dissolved, and total contents of soil
nutrient elements!
23. What is cation exchange? Explain all the factors controlling this reaction in the soil
system!
24. Explain the dissolution of precipitates of carbonates, sulfates, sulfide, and phosphates!
25. Explain the most important factors controlling the concentrations of free nutrient
elements in soil water!
26. Explain the importance of soil pH in controlling the dissolution process in the soil
environment!
27. What is soil E? How does this variable control the dissolution of FeS and Fe 2 (HPO 4 ) 3 ?
28. Explain the weathering of orthoclase! Explain also all the factors controlling this
reaction!
29. Explain the importance of pH in controlling the weathering of primary minerals!
30. Explain how the soil organic matters decompose and release nutrient elements in the
soil environment! What nutrient elements are released?
31. Explain all the factors controlling the soil organic matter decomposition!
32. Explain the importance of water and enzymes in the soil organic matter decomposition!
What about other factors like soil pH, soil T, and soil C/N ratios?
33. How does the soil pH affect the activities of phosphatases?
34. Explain how weeds directly and indirectly influence the soil chemical properties!

Abdul Kadir Salam and Nanik Sriyani – 2019