Effects of Forest Conversion
B. Pineapple Plantation
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The Chemistry and Fertility of Soils under Tropical Weeds 69
in relation to the decrease in soil C content (Table 4.6). Salam (1999) also report that the availabilities of micronutrients in the same locations also decreased by land-use conversion, in correlation with the decrease in soil organic C, total N, and CEC (Salam, 1999). Salam et al. (1999b) also document that the available P decreased by land-use conversion from bushes to sugarcane and pineapple plantation (Table 4.7). The available P in bushes is higher than those in soils monoculturally planted with sugarcane or pineapple.
Table 4.7. The available P in sugarcane and pineapple plantations of Central Lampung Indonesia* (After Salam, 2014).
No Period of Cultivation (Years)
Available P (mg kg-1) A. Sugarcane Plantation:
1 0** 8.44
2 3 7.19
3 9 8.16
4 13 23.1
5 20 63.6
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70 The Chemistry and Fertility of Soils under Tropical Weeds
and exchangeable K were significantly higher in the secondary forest and the plantation than that in the intensively cultivated land like the cassava and the paddy fields. For example, the organic C and CEC in the forest of Mulyasari were 36.6 g kg-1 and 14.3 cmolc kg-1 while those in the cassava plantation were 9 g kg-1 and 4.9 cmolc kg-1, about 25% and 34%, respectively. The land-use conversion in Tulung Boho Central Lampung also showed similar pattern (Table 4.9). The soil pH, Organic C, CEC, and Exchangeable K were higher in the secondary forest than those in the other land-use systems. The organic C and CEC in the cassava plantation were much lower than those in the secondary forest, about 53% and 18%, respectively. Salam et al. (1999a) also report that the soil CEC and exchangeable K are well correlated with the soil Organic C with r = 0.68 and 0.63, respectively, indicating the importance of soil Organic C.
Table 4.8. The changes in some soil properties by land-use conversion in Mulyasari Central Lampung*.
Land-Use pH Organic C
(g kg-1)
CEC (cmolc kg-1)
Exch. K (mg kg-1)
Secondary Forest 5.2 36.6 14.3 73.4
Rubber 5.0 20.9 12.5 38.4
“Sengon” 4.4 11.7 5.6 29.5
Mixed Graden 4.5 21.4 6.8 58.1
Cassava 4.3 9.0 4.9 8.42
Cassava and Corn 4.5 13.8 5.7 29.5
Paddy 4.4 13.4 5.1 8.42
*Adapted from Salam et al. (1999a)
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Table 4.9. The changes in some soil properties by land-use conversion in Tulung Boho Central Lampung*.
Land-Use pH Organic C
(g kg-1)
CEC (cmolc kg-1)
Exch. K (mg kg-1)
Secondary Forest 4.8 24.9 25.9 62.4
Swamp 3.9 19.4 7.7 74.1
Pineapple 4.0 11.8 4.7 3.9
“Sengon” 4.4 16.7 2.7 31.2
Mixed Garden 4.0 10.4 3.1 42.9
Cassava 4.1 13.2 4.7 62.4
Corn 4.7 9.7 1.7 23.4
*Adapted from Salam et al. (1999a)
Key Questions
1. Explain the magnitude of land-use conversion in West Lampung in the period of 1978 - 1984 – 1990? What happen to the primary forest, secondary forest, monoculture plantation, residential areas, etc.? What is your prediction now and in the near future?
Explain!
2. What are the effect of land-use conversion on plant covers, weed dominance, and soil chemistry and fertility? Explain!
3. What are the effects of land-use conversion on the soil enzymatic activities? Explain!
4. What was the vegetation dominating the primary forest and the secondary forest?
Explain!
5. Explain the effects of long-term land cultivation with cassava on the soil chemistry and fertility!
6. Explain the effects of narural vegetation and Paspalum conjugatum on the soil enzymatic activities in coffee plantation of West Lampung!
7. Why do the living things such as microorganisms, macroorganisms, and plant roots produce enzymes? What enzymes are produced by these living things?
8. What is the function of soil enzymes? Explain their roles in nutrient cycles!
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72 The Chemistry and Fertility of Soils under Tropical Weeds
9. Explain the lifetime of soil enzymes in relation to proteases existing in the soil environment?
10. Does deforestation affect soil enzymes? Explain!
11. Explain the magnitude of the soil enzymatic activities in different land-use system like primary forest, secondary forest, monoculture plantation, and cultivated land!
12. Explain the difference of soil enzymatic activities in wood land versus meadow and cornfield!
13. Explain the relationship between the functions of plant roots and the soil enzyme production!
14. Explain the effect of fire on enzymatic activities!
15. Explain the effect of soil water content on the soil enzymatic activities! Does it relate to the existence of the enzyme producers?
16. How is the relationship between the soil total N and the organic C content with the soil enzymatic activities? Explain why!
17. Explain the effect of the existence of weeds in coffee pantation on the soil enzymatic activities!
18. How does the forest converstion affect the optimum pH of phosphatase? What is optimum pH?
19. How is the effect of Cu on the optimum pH of phosphatase?
20. How does the soil pH affect the soil enzymatic activities? Explain the chemical reasons behind this phenomenon!
21. How does the soil pH affect the soil phosphatase activities? Explain the chemical reasons behind this phenomenon!
22. What is the effect of CaCO3 on urease activities! Why?
23. What chemical properties are affected by land-use conversion? Why?
24. How does the land conversion affect the soil micronutrient metals in the soil environment?
25. Explain the relationship between the soil organic C and total N with the soil CEC and exchangeable K!
Abdul Kadir Salam and Nanik Sriyani – 2019