Page 129 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 117

acid that may decrease the soil pH. However, S powder is more expensive than
lime materials and, therefore, soil acidification is relatively expensive. An effective
application of S powder is of great importance. The best way is to apply a local
treatment in a limited sites. By this method, S powder will acidify only a small area
of soils needed for plant growth. As mentioned in the previous part, acidification is
not applied to acid soils. Depending on the purpose and need for agriculture
management, acidification may also be applied to acid soils as was conducted in
the plantations of Great Giant Pineapple in Central Lampung, Indonesia (Salam et
al., 1998e).

Important Questions

1. What are the two major variables controlling the soil chemical properties and
reactions?
2. Mention some natural and anthropogenic reactions in the soil system that may
acidify soils!
3. How can carbondioxyde that is produced during the respiration by soil organisms
decrease the soil pH? Explain! Can the change affect the soil enzymatic activities?
4. How can long-term use of Urea decrease the soil pH? Explain! Can the change affect
the soil enzymatic activities?
5. Explain the role of cation exchange processes in the soil acidification by long-term
use of Urea!
6. How can S powder acidify soil? Explain! Can the change affect the soil enzymatic
activities?
7. Mention some chemical reactions in the soil system that may increase the soil pH!
8. How can lime materials increase the soil pH? Explain! Can the change affect the soil
enzymatic activities?
9. How can P fertilizers increase the soil pH? Can the change affect the soil enzymatic
activities?
10. Explain the relationship between the soil enzymatic activities and soil pH!
11. Explain the relationship between the soil phosphatase activity and soil pH!
12. What is Optimum pH for soil enzymatic activities?
13. Do the forest clearing and conversion to other land-uses change the optimum pH?
14. Are the Optimum pH different with locations of soil sampling? Explain!
15. Explain the procedure of analysis of phosphatase activity in soils! Explain the
function of each step and each chemical used!
16. Why is the pH important in the soil enzymatic analysis? Explain! What is the
importance of Optimum pH for enzyme analysis?

Abdul Kadir Salam - 2014