African agroforestry systems enhancing carbon storage maintain sustainability and mitigate climate change. How much carbon? That’s matter!
Tree and crop intercropping systems are both indigenous and introduced agroforestry systems common in sub-Saharan Africa. Intercropping can enhance soil organic matter, and thereby carbon (C) sequestration, can increase resilience to drought in sub-Saharan Africa, and contribute to climate change mitigation. Also, soil C sequestration can provide additional economic benefits to agricultural communities through C trading schemes.
Due to a lack of information on soil C sequestration and greenhouse gas (GHG) carbon dioxide (CO2) emission in intercropping systems, it is difficult to accurately quantify their potential to mitigate climate change. Our current understanding of soil C sequestration and soil GHG emissions in sub-Saharan Africa is very limited compared to the potential that the region has as both a sink and source for C and soil GHG emissions.
In this proposed study, soil C sequestration and soil CO2 emissions will be quantified to determine net soil C gain (the potentials of mitigating global warming) in established intercropping systems in Ethiopia, Uganda and Malawi.
The estimated net soil C gain in tree-crop intercropping systems will be useful for local communities and extension staff to understand the roles of intercropping systems for improving soil fertility and enhancing resilience to increased drought caused by climate change. Also, the results will help local communities and extension staffs participate in C trading schemes and provide additional economic benefits to agricultural communities.
This study will provide critical information to improve our understanding of soil C sequestration and soil CO2 fluxes from a large geographical region of the world for which little information presently exists. This work should also help to improve global climate change models for predicting climate change in sub-Saharan Africa and around the world.
What actions do you propose?
Growing crops among various tree species has been traditionally practiced throughout tropical regions (Kumar and Nair, 2006). Ethiopian indigenous home garden systems are a representative example of an intercropping system. Home garden systems are defined as a small-scale food production system, composed of a high diversity of plants, and located near to the residence (Sustainable Land Use Forum, 2006). Home garden systems provide households with wood, food, fodder and cash (Abebe, 2005) and the high diversity of species in these systems contributes to genetic conservation of native species, efficient resource use, biological pest control and environmental services such as control of soil erosion and maintenance of soil nutrient levels (Kippie, 2002).
Ethiopian home gardens grow crops such as ensete (Ensete ventricosum) and coffee (Coffea arabica) that can coexist with various tree species. Photo: D.-G. Kim
Nitrogen (N)-fixing tree and crop intercropping systems in sub-Saharan Africa, including those in Malawi and Uganda, are other examples of tree and crop intercropping systems. The N-fixing trees such as Sesbania sesban (L.) Merr. and Gliricidia sepium (Jacq.) Walp. provide natural N fertilizer for growing crops, making farmers less reliant on synthetic N fertilizers for their cropping (Makumba et al., 2006). For example, in southern Malawi, maize yield gains with Gliricidia-maize intercropping system have been shown to double in a trial established in 1991 (Akinnifesi et al., 2010).
Established Gliricidia-maize intercropping system in Southern Malawi. Photo: T. Breedy
Currently, drought-driven famine threatens nearly 12 million people in sub-Saharan Africa. Global climate models predict an increased chance of summer drying on the African continent in a future warmer climate with increased risks of prolonged drought (Dai, 2011). Soil organic matter (SOM), including soil C, is a key to drought-resistant soil and sustained food production since SOM increases infiltration and water holding capacity of soil and also reduces run-off (Zeiger and Fohrer, 2009). Tree and crop intercropping systems can increase SOM and accelerate C sequestration in soil because the organic matter (OM) assimilated by woody perennials is transferred belowground via root growth and OM turnover processes such as fine root dynamics, rhizo-deposition and litter dynamics (Beedy et al., 2010). Therefore, by increasing SOM through intercropping practices enhanced resilience to increased drought caused by climate change can be achieved. In addition, sequestration of CO2 as soil C is one of the promising strategies to mitigate climate change (IPCC, 2006). Therefore, intercropping practices can also contribute to mitigating climate change. Through Reduced Deforestation and Forest Degradation (REDD+), C sequestration in intercropping systems can provide additional economic benefits to agricultural communities (Jindal et al., 2008). Overall, intercropping systems that enhance soil C sequestration in sub-Saharan Africa can provide farmers increased resilience to climate change, and additional economic benefits, as well as contribute to mitigating climate change.
Mean air temperature of Afican countries (1971-2000). Source:The Center on Climate Change and Instability in Africa
Information is lacking on soil C sequestration in intercropping systems. Also, there is a concern about the effect of the intercropping systems on soil C loss from soil CO2 emission. In southern Malawi, soil CO2 emissions from a Gliricidia-maize intercropping system were up to three times higher than emissions from a sole-maize cropping system due to an accumulated organic layer and the extensive tree root systems (Makumba et al., 2007). These results suggest that other intercropping systems may also increase emissions of CO2 from soil in contrast to a mono-cropping system, and this may negatively affect the expected benefits of soil C sequestration by reducing net soil C gain (soil C gain as C sequestration − soil C loss as soil CO2 emissions) in these systems. Due to lack of information on soil C gain from soil C sequestration and soil C loss from soil CO2 emissions in the intercropping systems, it is therefore difficult to accurately quantify the potential benefits from net soil C gain. This causes uncertainties in global GHG research (Yohannes, 2011) and difficulties in soil C trading for local agricultural communities (Bryan et al., 2010).
The main scope and objectives of this study are 1) to indentify an appropriate technology and protocol for determining soil C sequestration and soil CO2 emissions in Ethiopia, Uganda, and Malawi, 2) to determine the net gain of soil C in established intercropping systems in Ethiopia, Uganda, and Malawi and 3) to provide information and training for local communities and extension staff to successfully participate in carbon trading schemes.
First, this study will develop an appropriate technology and protocol which can be easily adapted and utilized for determining soil C sequestration and soil CO2 emissions in Ethiopia, Uganda, and Malawi. Determining soil carbon sequestration and soil CO2 emissions requires high precision sensors and analysers and advanced technologies to calibrate, operate and maintain the sensors and analysers. Also it requires a well prepared protocol clearly indicating detail processes for complex situations in different soil properties, environment and weather conditions. While high precision sensors and analysers and advanced protocols are recommended to achieve accurate results, they are not affordable by most developing countries. Also, supporting technical services and materials are not available in the countries. Therefore, for developing countries, it is important to identify an appropriate technology and protocol which can provide acceptable accuracy and precision within an affordable cost range and with available technical service and materials. In this study, we aim to identify these appropriate sensors and analysers and develop protocols which can be easily utilized in Ethiopia, Uganda, and Malawi.
Vegetation and environment survey in home garden. Photo: D.-G. Kim
Soil sampling and survey in home garden. Photo: D.-G. Kim
Processing collected soil samples. Photo: D.-G. Kim
Soil emitted greenhouse gas sampling in home garden. Photo: D.-G. Kim
Second, through quantifying C gain from soil C sequestration and C loss from greenhouse gas CO2 emissions, the net gain of soil C will be determined in established intercropping systems in Ethiopia, Uganda, and Malawi. For the processes, we will focus on understanding the spatial variation of soil C stocks and control factors and spatial and temporal variation of soil CO2 fluxes including the potentially abrupt increases in soil CO2 emissions at the beginning of rainy seasons. We will also accurately quantify annual soil CO2 emissions. This study will provide critical information to improve understanding of soil C sequestration and soil CO2 fluxes from a geographical region for which little information presently exists.
Third, this study will provide information and training for local communities and extension staff to successfully participate in carbon trading schemes. On-farm demonstration projects and workshops will be held for local communities and extension staff. Through these demonstrations and workshops, local communities and extension staff will receive information and training to develop their own specific protocols for developing collaboration with research institutes to participate in C trading schemes.
On-farm demonstration for local communities and extension staff in home garden. Photo: D.-G. Kim
Who will take these actions?
Principal investigator (PI) Dr. Dong-Gill Kim received his Ph.D at Iowa State University, Iowa, USA in 2008 and he has been working as Assistant Professor at Hawassa University, Ethiopia. Dr. Dong-Gill Kim will manage studies in Ethiopia, Dr. Patson Cleopus Nalivata (Lilongwe University, Malawi) will manage studies in Malawi and Dr. Moses Tenywa (Makerere University, Uganda) will manage studies in Uganda. In addition, Northern researchers from USA will participate in the study. Dr. Rich Conant (Colorado State University, USA) will supervise experimental design, measurement, data management and interpretation and publication. Dr. Richard Schultz (Iowa State University, USA) will join the study as an international expert in Agroforestry and soil conservation. Through collaboration between three different sub-Saharan African countries and Northern countries, knowledge interactions will be strengthened and outcomes of the study will be effectively disseminated globally.
The collaboration between these local agricultural communities and the institute will be useful for both promoting active involvement of local communities in the practice of intercropping and participating in C trading schemes. Lilongwe University in Malawi, Makerere University Agricultural Research Institute in Kabanyolo, Uganda and Hawassa University in Ethiopia have all been promoting the use of tree and crop intercropping systems. These institutes can play a key role in training local communities and extension staff, and can conduct the analytical and scientific work needed. Collaboration between the institutes and local communities can be a successful model for measuring and reporting soil C sequestration and soil CO2 emissions that can be expected from intercropping systems.
Where will these actions be taken?
The study will be conducted in three different sites in each of three countries in sub-Saharan Africa: 1) Gedeo zone, Southern Ethiopia, 2) Zomba, Malawi and 3) Kabanyolo, Uganda.
In Ethiopia, the study will be conducted in the Gedeo zone (6o 20’ N, 38o19’ E). The Gedeo home gardens fall into three categories: 1) enset-tree systems; 2) enset-coffee-tree systems; and 3) coffee-fruit crops-tree systems. This study will include three replicate plots (plot size 30 m × 30 m) of each of these 3 major home garden types and three replications of control sites of fertilized mono-crop systems (i.e., enset or coffee only; plot size 30 m × 30 m). The control sites will be adjacent to the treatment home gardens and have the same age structure as those gardens.
In Zomba, Malawi, the study will be conducted at Makoka Agricultural Research Station (15o 30’ S, 35o15’ E). A long-established trial with Gliricidia-maize intercropping will be assessed. The trial was established in December 1991 and it is composed of sole-maize cropping plots and Gliricidia-maize intercropping plots. For this study, three of Gliricidia-maize intercropping plots (30 m × 30 m) and 3 of control sites of fertilized mono-crop systems (30 m × 30 m) with the same age structure as the treatment Gliricidia-maize intercropping plot will be randomly selected.
In Kabanyolo, Uganda, the study will be conducted at Makerere University Agricultural Research Institute (0o 28’ N, 32o 37’ E). A long-established trial with Gliricidia-maize intercropping (established in 1991) will be used. Three of Gliricidia-maize intercropping plots (30 m × 30 m) and 3 of control sites of fertilized mono-crop systems (30 m × 30 m) with the same age structure as the treatment Gliricidia-maize intercropping plots will be randomly selected.
Study sites: Ethiopia, Uganda and Malawi. Map: D.W. Ko
How much will emissions be reduced or sequestered vs. business as usual levels?
There is possibility of mitigating greenhouse gas emissions through agroforestry compared to mono-cropping. Mono-cropping degrades soil fertility with losing soil organic carbon and also produces greenhouse gas due to intensive soil disturbance and synthetic fertilizer application. In contrast, agroforestry practices can increase soil organic carbon through organic matter provided by tress growing with crops. Also they can reduce greenhouse gas emissions since soil disturbance and synthetic fertilizer application can be minimized. An annual net gain of soil C of 3.5 Mg C ha-1 yr-1 is estimated in tree and crop intercropping systems (Kim, 2012). However, due to lack of the quantified information, the potential of the mitigation through agroforestry has not been well understood. The results of this study will provide evidence of the potential of agrofestry for mitigating climate change, and also provide communities with scientific data to participate in C trading schemes.
What are other key benefits?
Through on-farm demonstrations, local farmers and extension staff will improve their understanding of how tree-crop intercropping systems contribute to enhancing soil C sequestration. This will be useful for developing and conducting future studies to monitor changes in the practices that they make later.
A policy brief will be provided to higher level policy and decision makers to engage them in dialog and provide policy options on appropriate intercropping practices. It would also help policy-makers in African countries facilitate entry into the carbon-market.
Our current understanding of soil C sequestration and soil CO2 emissions in sub-Saharan Africa is very limited compared to the potential that the region has as both a sink and a source for C and soil CO2 emissions. Through this study, critically important information including temporal variation of soil C dynamics, control factors and spatial and temporal variation of soil CO2 fluxes will be obtained.
What are the proposal’s costs?
This study will be carried out by three different research teams from Ethiopia, Uganda and Malawi for three years and it requires $450,000.
The cost will be required to support 1) graduate assistants, 2) instrument, materials and supplies, 3) field data collection, 4) on-farm demonstrations, workshop and seminar, 5) travel and presentation at international conferences, 6) publication and report.
It will require $50,000 per a year and a team and it will totally cost $450,000 ($50,000 per year and a team x 3 years x 3 teams = $450,000).
Detail lists of the item are provided as below:
1) Graduate assistants
A MSc or Ph.D student for each team; involved in field measurements, data analysis, presentation and publication
$5000 per a year and a person
2) Instrument, materials and supplies
Purchasing and maintaining soil CO2 measurement system, soil microclimate monitoring system, and soil sampling tool; conducting soil analysis
$20000 per a year and a person
3) Field data collection
Researchers will visit study site regularly (minimum weekly) to collect soil samples and soil CO2 flux measurements
$10000 per a year and a team
4) on-farm demonstrations, workshop and seminar
On-farm demonstrations, workshop and seminar will be opened for local farmers, extension staff and researchers
$5000 per a year and a team
5) Travel and presentation at international conferences
A local PI or a graduate research assistant will attend an international conference
$6000 per a year and a team
6) Publication and report
Research Blog, web based open database, You tube video clips, annual reports, working papers and peer-reviewed papers
$4000 per a year and a team
This study will be carried out by three different research teams from Ethiopia, Uganda and Malawi for 3 years (36 months). Major activities in each year are listed as below:
- 1st year
Site selection and sensors and analysers set-up,
Research Blog and Youtube page set-up,
Starting soil CO2 flux measurement,
- 2nd year
Continuing soil CO2 flux measurement,
Starting soil carbon stocks measurement,
- 3rd year
Continuing soil CO2 flux measurement,
Continuing soil carbon stocks measurement,
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