沙漠研究 19-1, 351- 354 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Approaches of Agroforestry Management in the Central Ethiopia
Masku DERESSA1, Kiyoshi SHIRATORI2, Iwao MATSUMOTO2, Berhanu S. JABESSA1,Shinji SUZUKI3, Yukimitsu KOBAYASHI3, Satoru TAKAHASHI3
Abstract: Life of the people in the central rift valley areas of Ethiopia depends on mixed
agriculture with main focus of livestock followed by crop production. Overexploitation suchas overgrazing and deforestation for fuel wood harvesting and crop production resulted insignificant degradation of natural resources in the region. A farmer research group (FRG) has
initiated to disseminate the agroforestry in the region for conservation and remediation of thenatural resources. As the first step to establish an appropriate management system of theagroforestry suitable for the regional climate and social condition, it is required to collectpractical information concerning selection of tree species and determination of planting density.
In the current study, a trial site of the agroforestry was set up in the region, survival rate of trees
integrated was examined, and the effect of agroforestry on micro meteorology was observed.
Acacia salicina showed the highest survival rate, and it is revealed that the agroforestry at thetrial site had a potential to mitigate evaporation and extreme increasing of temperature. The
FRG organized in the current study has enhanced the farmers’ capacity to utilize their inherent
experience for innovative actions in the agroforestry management.
Through thoseparticipatory approaches of farmers, strategies for sustainable production system of theagroforestry will be developed.
Keywords: Agroforestry, Ethiopia, Micro meteorology, Participatory approaches of farmers,
Rift valley area

1. Introduction
Central rift valley areas in Ethiopia is classified as semi-arid with annual rainfall ranging from 500 to700 mm, high temperature, high wind speed, and less biodiversity, while the life of the people depends on
mixed agriculture with main focus of livestock followed by crop production. Natural resource in the area
is scarce and fragile. Therefore, overexploitation such as overgrazing, deforestation, and subsequent soil
erosion is a major cause for the deprived condition resulting in the livelihood of rural people being
significantly affected (IIRR, 2002). In Ethiopia, wood harvesting exceeds the replanting which leads tothe decline of forest resource (Ethiopia Forestry Strategy, 2001). The forest coverage in Ethiopia was
40 % in 1900’s, dropped down to 16 % in 1950’s and only 2 – 3 % in 1990’s. In Oromia state, one of thestates of Ethiopia which dominantly covers the central rift valley area, 60 to 100 thousand ha of forest are
depleted every year for fire wood, charcoal and land clearance for crop production thus affecting the soilsurface vegetation and the whole ecosystem in the area (EFAP, 1994). Therefore, it is suggested thatcombining crop production with tree planting (i.e. agroforestry) would result in an effective measure forconservation and remediation of the natural resources. In order to solve these problems we haveorganized a farmer research group (FRG) and initiated to disseminate the agroforestry in the region.
However, appropriate management system of the agroforestry suitable for the regional climate and social
condition has not been established due to lack of practical information. In the current study ourapproaches in the agroforestry management, particularly addressing to planting trees, are discussed basedon physical environment observation.
2. Material and Method
The study site is located in the central rift valley of the Oromia state (7˚49’N and 38˚42’E). The
mean annual rainfall, mean annual maximum temperature, and mean annual minimum temperature in thearea over the past 20 years were 704 mm, 27.8 ˚C, and 13.4 ˚C, respectively. Soil type of the site is loamy
1Adami Tulu Agricultural Research Center, P. O. Box 35, East Shewa Zone, Ziway, Ethiopia.
E-mail: dayitur@yahoo.com
2
Japan International Cooperation Agency, P. O. Box 436, Adama, Ethiopia.
3
Tokyo University of Agriculture, 1-1-1, Sakuragaoka, Setagaya, Tokyo, 156-8502, Japan.

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sand. The site was under repeated maize cultivation before the study. In 2005, around 180 seedlings
were randomly transplanted in 18.8 m × 15.8 m area with 1 m spacing after planting holes with 30 cm
diameter and 60 cm depth were made. Major tree species established was Acacia salicina (40 %)followed by Casuarina equisetifolia (25 %), Azadirachta indica (22 %), and Grevillea robusta (13 %).
Those species were selected after observational evaluation made on farmers’ agricultural land to assess
their contribution and adaptability to the agroforestry. Trees were aligned east to west to allow sunlightfor the crops. Supplemental irrigation was undertaken when required.
Survival rate was observed for each species in June 2006. Both inside and outside the agroforestry,
air temperature, relative humidity, solar radiation, and albedo were recorded in the dry season (December,2007) and rainy season (August-September, 2008) in order to quantify differences in the environment
between inside and outside agroforestry and to assess the effect of the agroforestry on micro-meteorology.
The air temperature and relative humidity sensor used was TR-3110 (T&D Co., Japan) and the data wasrecorded by a data logger (TR-72U, T&D Co., Japan) and installed at a height of 1.5 m with a solar
radiation sealed. Solar radiation and albedo were measured using the pyranometer with the light meter(LI-200SA and LI-250A, LI-COR, USA).
3. Results and Discussion
The highest survival rate was observed for Acacia salicina (91.5 %), followed by Azadirachta indica(87.5 %), Casuarina equisetifolia (86.4 %), and Grevillea robusta (83.3 %) (Table 1). Major reason ofvariability in the observed survival rate between species is suggested to be differences in drought toleranceof the species.
Table 1. Survival rate of tree species established in the central rift valley, Ethiopia.

Name of species

Number ofplanted (trees)

Number of deadtrees (trees)

Survival rate (%)

Acacia salicina

71691.5

Casuarina equisetifolia

44686.4

Azadirachta indica

40487.5

Grevillea robusta

24483.3

Table 2. The effect of agroforestry established in the central rift valley on receiving and reflecting solarradiation.

Dry season(14:00-15:30
Dec. 10, 2007)
Rainy season(15:10-15:35
Sep. 1, 2008)

Radiation

Reflection

W/m2

W/m2

Inside

325

64

0.25

Outside

717

152

0.21

Inside332

840.29Outside

801

162

0.20

AlbedoThe solar radiation inside the agroforestry was less than a half of that observed outside, indicating thataround 41 to 45 % of the solar radiation reached inside the agroforestry (Table 2). In contrast with this,relatively larger albedo was observed inside of the agroforestry in both dry and rainy season compared tothe outside resulting in reduced ground temperature and, in particular, evaporation from soil surface.
In dry season (December, 2007), extremely high temperature (up to 35 ˚C) and low relative humidity

353(down to 3 %) were recorded outside the agroforestry at the daytime, while moderate temperature (up to 27
˚C) and humidity (down to 10 %) observed inside (Fig. 1). Contrasting this, air temperature outside theagroforestry decreased below 10 ˚C at night-time, while it was warmer inside the agroforestry (Fig. 1).
Differences in the temperature during the daytime were due to differences in the amount of solar radiation
between the inside and the outside (Table 2), and it is suggested that the canopy of trees reduced long wave
radiation from the ground to the atmosphere during night-time.
In the rainy season (August, 2008), daily maximum air temperature observed in the agroforestry waslower by around 27 ˚C than that observed at outside the agroforestry, while there was less difference in thedaily minimum air temperature between outside and inside the agroforestry (Fig. 2). Although the daily
maximum temperature of outside in dry season is higher than that in rainy season, daily mean temperaturein dry season is lower than that in rainy season due to decreased daily minimum temperature. It is of notethat only slight differences in the daily mean air temperature were observed at inside the agroforestry
between the dry and rainy seasons.
Inside (Temp.)
Outside (Temp.)
Inside (RH)
Outside (RH)

8030602040

1020

RH (%)

Temperature (ﾟC)

40000:00
6:00
12:00
TimeFig. 1. Comparison of changes in air temperature and relative humidity (RH) between inside and outside theagroforestry observed on December 14-15, 2007.

18:00

35

100

30

80

2560

2040

RH (%)

Temperature (ﾟC)

12:00

15

Inside (Temp.)
Outside (Temp.)
Inside (RH)
Outside (RH)

100:00

6:00

200

12:00
18:00
0:00
TimeFig. 2. Comparison of changes in air temperature and relative humidity (RH) between inside and outside theagroforestry observed on August 30, 2008.

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However, there is a concern that the amount of solar radiation inside the agroforestry would beinsufficient for crop production due to high planting density.
4. Conclusions
In the central rift valley area, farmers had depended only on natural vegetation or commercial fuelwood and charcoal for domestic consumption. It is widely acknowledged that bringing about the process
and conditions that enable agroforestry technology to be productively used by the poor is extremely
difficult in developing countries like Ethiopia, where limited and ever shrinking land resource is ongoingby human population growth. Even in such difficulties however, there seems a tiny pocket of successfrom which we can derive lessons. For instance, the farmer’s research group (FRG) we organized in thestudy has enhanced the farmers’ capacity to utilize their inherent experience for innovative actions in theagroforestry management. Agroforestry is new experience for the farmers and by this work they will findits benefit through the practices. Indeed, there were wide agroforestry advantages investigated in thecurrent study that calls our attention to plant trees. In the current study, it is revealed that the agroforestry
at the trial site had a potential to mitigate evaporation and extreme increasing of temperature. The resultsfrom the current study will be used for determination of an adequate planting density. Other benefit of theagroforestry is expected to be increasing soil organic matter resulting from the biomass, low competition offertilizer extraction between trees and crops, and high quality building materials due to upright growth oftrees. Establishment of the agroforestry in the central rift valley could also potentially influence
rehabilitation of the natural environment including carbon sequestration.
Finally it is strongly recommended to set strategies of on farm sustainable production and distributionof tree seedlings by farmer to farmer. It is also important to establish cost and labor sharing system andthis can be achieved through participatory approaches of farmers.
References
International Institute of Rural Reconstruction (IIRR) (2002): Managing dry land resources -An extension manual for eastern andsouthern Africa. International institute of rural reconstruction, Nairobi, Kenya.