dynamics of soil carbon sequestration under oil palm plantations of different ages

GSOC17 - Global Symposium on Soil Organic Carbon21-23 March 2017 - FAO HQ - Rome, Italy

DYNAMICS OF SOIL CARBON SEQUESTRATION UNDER OIL PALM PLANTATIONS OF DIFFERENT AGES

ByBrahene Sebastian Wisdom



PRESENTATION OUTLINE

Introduction Background information Problem statement Justification Objectives

Materials and Methods Results and discussion Summary, conclusion and

recommendations



INTRODUCTIONBACKGROUND INFORMATION

Tackling climate change demands special attention to agriculture (Smith et al. 2008).

Oil palm cultivation in Ghana BOPP, GOPDC, TOPP, Smallholders Conversion of forests and C losses



INTRODUCTION CONT’D

Oil palm cultivation and activities pruning and heaping of palm

fronds in between the rows of plants.

Beneficial effects of prunning and heaping Ensure clean farms to undertake

other farm operations such as harvesting, rodents control, etc.



INTRODUCTION CONT’DPROBLEM STATEMENT

Evidence is thin on soil carbon studies under pruned palm frond heaps on

smallholder oil palm plantations in Ghana.



INTRODUCTION CONT’DJUSTIFICATION

There is therefore the need to quantify the soil carbon dynamics in a false chrono-sequence under

pruned fronds heaped on smallholder farms in Ghana.



INTRODUCTION CONT’DOBJECTIVES

1. To assess soil C content and stocks under pruned heaps in already established oil palm plantations of different maturity ages;

2. To examine the dynamics (changes) in soil C stocks over time under pruned heaps in these oil palm plantations.



MATERIALS AND METHODS Study sites: private smallholder farms within the

same agro-ecological zone

Site selection five clusters according to age of oil palm plantation Questionnaire Multi-stage sampling for further grouping

Top, Middle and Bottom slopes Modal instance sampling

Bottom slope Eight farms were targeted snow balling Random sampling

Sampling costs and locations



MATERIALS AND METHODS CONT’DSAMPLED PLOTS



MATERIALS AND METHODS CONT’D Sample collection and preparation

Sampling area: 25X25m Sampling depth: 0-10, 10-20 cm Uniform depth increments rather than by pedogenic

horizons Sampling spots

1. Alleys between rows of palm trees 2. Under pruned heaps of palm branches

Sampling was preceded by grid marking 72 samples Core samplers for undisturbed samples Composite sample Soils air dried , crushed and sieved through a 2 mm

sieve for laboratory analyses



MATERIALS AND METHODS CONT’D

Calculating for C stocks

Carbon stocks were determined on the fine earth fraction after bulk density and C content had been determined on the soils using the formular below:

C stocks (Mg ha-1) = ρb (Mg/m3) × C content (kg/kg) × a (m2) × d (m)

Where ρb- Bulk densitya- Area of a hectard- Sampling depth



MATERIALS AND METHODS CONT’D Calculating carbon saturation deficit

Adopted from van Noordwijk et al. (1997) Carbon saturation deficit was calculated from

stocks using the formular below:Csatdef = [(Cref-Corg)/ Cref] ×100%Where Cref- Carbon stock in reference soilCorg -Current carbon stock in soil

Data Analyses Genstats (12th edition) and Minitab (16th edition)

were used for computer analysis.



RESULTS AND DISCUSSION



RESULTS AND DISCUSSION CONT’D

A notable drop in OC within the first 5 years upon cultivation was seen as has been reported by by Guo and Gifford (2002).

The subsequent drop in OC beyond 10 years was gradual (Lamade et al., 2005) when compared to the 5-10 years group but less than 15 % of that for previous years as was observed under alleys with age.

Soils under these heaps had termites, beetles and other organisms except earthworms due to the vertical migration of these organisms to areas of more moisture and so affected C turnover in deeper layers instead (Briones et al. 1998a, 2010).



RESULTS AND DISCUSSION CONT’D

C stocks followed a similar trend as OC values with the 20-25 year group under pruned fronds obtaining a maximum of 25.2 Mg C/ha.

The value of 59.6 Mg C/ha calculated for the 0-20 cm layer under forest conditions (uncultivated) in this work falls within the range 5-180 t/ha for the 0-30 cm layer as put out for humid tropical forests (IPCC, 1997).



RESULTS AND DISCUSSIONS CONT’DRELATIONSHIP BETWEEN C STOCK AND MANAGEMENT

OPTIONS

Carbon in soils within alleys was lower than that under pruned heaps. Cultural practices, C removal, erosion,

flooding

The system of adding pruned materials as residue to soil seems to improve the storage of carbon particularly in the 0-10 cm layer.

Management system seen as the main factor affecting stocks.



RESULTS AND DISCUSSION CONT’DRELATIONSHIP BETWEEN C STOCK AND MANAGEMENT OPTIONS



RESULTS AND DISCUSSION CONT’DRELATIONSHIP BETWEEN C STOCK AND MANAGEMENT

OPTIONS

Initial additions to soil were small but possibility of reaching equilibrium and exceeding is attainable beyond 25 year period.

In addition to the annual increases in stocks under prunnings, some organic materials are still present on the farm at various stages of decomposition.

Undecomposed materials serve as a means to trap and hold C and other gases (released via decomposition) which otherwise would have been emitted into the atmosphere contributing to greenhouse gases.



CONCLUSION AND RECOMMENDATION

The basic criteria for increasing SOC is that the amount of C added in residues, including plant roots, exceeds the amount of C lost in decomposition.

Thus quantifying the effects of individual management practices such as prunning and heaping of fronds and their combinations on C sequestration is vital for improving the potential of farming systems to sequester C.

The practical implications of this research would be to encourage prunning and heaping of palm fronds within rows of palm trees at well designated spots continually. This action would not only provide nutrients to the crops but would with time contribute to building C levels in the soils in addition to the pruned materials that would remain on top of the soil.

The study recommends research into how to improve decomposition of oil palm residue to enhance the fertility of the mineral soil as infiltration through the fronds becomes limiting with increasing height of heaps.


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dynamics of soil carbon sequestration under oil palm plantations of different ages

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