Adsorption–desorption and bioavailability of selected micronutrients in tropical peat soil in Sarawak, Malaysia
Tropical peatland has a distinctive bio-sequence of concentric forest zones with different forest types. Mature peat swamps in Sarawak comprised of mixed peat swamp forest (MPS), Alan Batu forest (A.Bt), and Alan Bunga forest (A.Bg). These forest types may differ in their decomposit...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/90642/1/FP%202019%2070%20-%20IR.pdf |
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| Summary: | Tropical peatland has a distinctive bio-sequence of concentric forest zones with different forest
types. Mature peat swamps in Sarawak comprised of mixed peat swamp forest (MPS), Alan Batu
forest (A.Bt), and Alan Bunga forest (A.Bg). These forest types may differ in their
decomposition of soil organic matter (SOM) contents, thus affect the availability of
micronutrients, since peat soils are generally oligotrophic. This study investigated the
availability of copper (Cu), zinc (Zn) and boron (B) to the plants under different forest types.
The adsorption and desorption batch experiment were performed using soil samples collected from
MPS, A.Bt and A. Bg forests. Further relationship between adsorption and desorption with
Cu, Zn and B availability in highly decomposed peat soil type (MPS) were examined in a
polybag experiment using Napier grass (Pennisetum purpureum) as the test crop. The adsorption data
of Cu were fitted better on the Langmuir’s model while Zn adsorption data were comparable between
the model used and B adsorption data was fitted better in the Freundlich’s
model. Generally, the Kf and b values were observed in order of Cu > Zn > B. This
shows that Cu has a high affinity towards the peat soils surface compare to Zn and B. The MPS
forest soils were observed to have slightly high adsorption capacity for Cu, Zn and B.
This could emphasize that more decomposed peat materials would influence the affinity of Cu, Zn
and B towards peat soil surface. Release of Cu, Zn and B was evaluated with different extractants
to determine the available, exchangeable and complex form of micronutrients. The complex
form of Cu and Zn is significantly different for MPS soil compare to exchangeable and available
form. Copper and Zn were observed to highly bind to the surface of peat soils and the stronger
chelating agent needed to desorb them into the soil solution. Release of B has shown no significant
differences among extractants used, since B has low affinity towards the soil surface and easily
leach out from the soil system. The application of Cu, Zn and B solution with
different concentration (0, 1, 3, 5, 10, 20, 30 mg L-1) to the Napier grass planted in peat soils
showed that mean dry matter yield has no significant difference among the treatment. The
polynomial plot showed the optimum uptake of Cu and Zn (in
range of 10 – 20 mg L-1) and B (up to 5 mg L-1). The mean uptake of Zn (0.52 mg plant-1) was higher
than Cu (0.11 mg plant-1) and B (0.064 mg plant-1) because Cu has a high affinity towards the soil
surface, while B easily leaches out to the soil solution system. Therefore, considering 4R (right
source, right rate, right time and right place) nutrient stewardship is important to the
improved nutrient use
efficiency of the plant. |
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