Determinants of sustainability in urban and peri-urban agriculture Andreas Buerkert, Eva Schlecht, Martina Predotova, Rodrigue V.C. Diogo , Katja Kehlenbeck and J. Gebauer Faculty of Organic Agricultural Sciences, University of Kassel, Germany Email: [email protected]
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Determinants of sustainability in urban and peri-urban agriculture
Andreas Buerkert, Eva Schlecht, Martina Predotova, Rodrigue V.C. Diogo , Katja Kehlenbeck and J. Gebauer
Faculty of Organic Agricultural Sciences, University of Kassel, GermanyEmail: [email protected]
Nutrient depletion and erosion of rainfed land
unfertilized controlplaced NPK
Effects of placed NPK application at 4 kg P ha-1 on millet growth in a farmer’s field (Maradi, Niger)
Buerkert et al. 2001. Field Crops Research 72, 1-15.
Buerkert et al. 1996. Plant and Soil 180, 29-38.
Nutrient poor soils as a major constraint to productivity
Based on data by UN Population Division, 2004.Pay Drechsel, Sophie Graefe, Moise Sonou and Olufunke O. Cofie, 2006. IWMI Research Report 102
Population growth and distribution in Africa- many causes one consequence -
• Unplanned and informal, often illegal settlements
• Inefficient infrastructure (water supply, energy supply, waste disposal, sewage)
• Pollution from urban wastes (household, industrial, traffic)
• Increased level of urban food insecurity and malnutrition
• Increasing urban poverty, accompanied by a widening income gap
Consequences of rapid urban growth
Who are urban agriculturalists?
• Migrants from rural areas
• Refugees
• Vulnerable groups in need of a social security strategy
• People with limited formal education
Smith 2001, IDRC
Extent of urban food production in Africa
44-70Dar-Es-Salaam (Tanzania)
30Mombasa (Kenya)
29Nairobi (Kenya)
80Harare (Zimbabwe)
36Ouagadougou (Burkina Faso)
75Kano (Nigeria)
Proportion of urban dwellers
involved in UPACity
Drechsel et al., 2006
Income effects of UPA along the marketing chain
DAAD
The UrbanFood – Research Network
FaisalabadPakistan
How to define sustainability? a need for indicators
Sustainability depends largely on interactions between social, economic and bio-physical components of the system!Economic
SocialBio-physical,
Ecological
Research goals and methodological approach
• Typology and classification based on satellite images and a (socio-economic) baseline-survey in six cities
• Measurement of matter fluxes (C, N, P, K balances)• Environmental effects and product quality
Multi-stepapproach
GoalsIncrease resource use efficiency based on process-oriented research on the functioning of (peri-) urban agriculture, matter fluxes, product contamination and negative externalities
1972 1987
2000 2005
Spatial development of UPA in Khartoum (Sudan)
Schumacher et al. 2009. Journal of Arid Environments (in press).
Modelled irrigation water use in Khartoum, Sudan
Schumacher et al. 2009. Journal of Arid Environments (in press).
28.51.2
28.40.64.88.3
Conc (mg l-1)a
5.0Pb0.2Ni0.1Cr0.2Mn5.0Fe2.0Zn
LimitsbMetals
a Kano State Environmental Planning and Protection Agencyb Pescod, M.B. 1992 Wastewater treatment and use in
agriculture. Irrigation & Drainage Paper 47, FAO, Rome, Italy
Quality of irrigation water in Kano (Nigeria)
Irrigation water characteristics
Soil loading with heavy metals in Kano, Nigeria
Zinc (Zn) Nickel (Ni) Lead (Pb) Copper (Cu) Cadmium (Cd)
050
100150200250300350
0-15
15-25
25-40
40-60
60-75
75-90
90-12
012
0-150
Depth in cm
Hea
vy m
etal
con
c.(m
g kg
-1)
Koki garden
050
100150200250300350
0-15
15-25
25-40
40-60
60-75
75-90
90-12
012
0-150
Depth in cm
Gada garden
Nafiu et al. (unpublished data)
A representative selection of UPA sitesis essential for a relevant extrapolation of results
Total N balances of UPA gardens- Example: Niamey, Niger -
(%)Total
Gaseous N lossesNH3 N2O
(kg ha-1 a-1)53 52 4848 59 41
92 32 68
(kg ha-1 a-1)
N leachingNO3-N
6*2*
7** values of rainy season 2007
Total Nbalance
(kg ha-1 a-1)310540
2,890
Diogo et al. (unpublished data).
Garden InputFertilizer Roots*
Output
——— (kg ha-1 a-1) ———River 1River 2
Sewage water
Gaseous C losses
Total CO2 CH4
(kg ha-1 a-1) (%)25,150 98 220,190 98 2
26,630 98 2
Horizontal C fluxes
* Estimated to be equivalent to the harvested shoot C
30,52012,280
7,820
2,2002,190
7,030
2,2002,190
7,030
Total C balances of UPA gardens- Example: Niamey, Niger -
Total C balance
(kg ha-1 a-1)5,270
- 7,910
- 18,810
N and C losses from dung storage in UPA gardens- Example: Niamey, Niger -
3 treatments / 4 repetitions
• Unprotected control (C)
• Roofed (R)
• Roofed + rock phosphate (RP)
Rainy season + hot dry season in 2007 (each 3,5 month)
Mixture of fresh dung heaped on 1 m2 metal tables installed with a slight slope to collect leachates
Gaseous N and C losses from dung storage in UPA gardens of Niamey, Niger
0
1
2
3
4RR+P
C
a Ba Aa B
ab A
a A
b AN
H3-
N (g
m-2
106d
-1)
SeasonHot dry Rainy
0
5
10
15
20
25
30
35
a Ab A
ab Aa A
a A
b B
CH
4-C
(g m
-210
6d-1
)
SeasonHot dry Rainy
0
1000
2000
3000
4000
5000
6000
a A
b Aab A
a Bb B
c B
CO
2-C
(g m
-210
6d-1
)
0.0
0.2
0.4
0.6
0.8
1.0
a A
a A
a A a Aa A
a A
N2O
-N (g
m-2
106d
-1)
Soil profiles in millet field versus UPA garden in Niamey
CEC(cmolc kg-1)
Soil
dept
h (m
)
ArenosolSadoré (Niger)
.
0 .2
0 .4
0 .6
0 .8
1 .0
0.2334.4
Corg(%)
PBray(mg kg-1)
pHKCl
1.10
0-0.2m
Fluvisol on river benchNiamey (Niger)
2.920.27416.1
CEC(cmolc kg-1)
Corg(%)
PBray(mg kg-1)
pHKCl
9.570.96416.7
Manure use in livestock keeping UPA households
0 5 10 15 20 25 30
Own millet field
Own vegetable garden
Own rice field
Selling to gardeners or intermediaries
Gift to neighbours or relatives
Collection in corral
Disposal to garbage
Number of households
Niamey Kabul
Fuel
Khartoum
Brick making
ConclusionsUrban and peri-urban agriculture (UPA) canmake an important contribution to supplyingfood and income opportunities to the raidlygrowing urban populations of developingcountries, but its role strongly varies betweenlocations.
• Negative externalities of UPA need careful analysis to derive effectiverecomendations fostering the sustainability of the systems.
• Carbon and nutrient balances strongly vary between and within locations. While N balances are often excessively possitive leading to N losses via volatilisation, C-balances heavily depend on the use of manure.
• A thorough unterstanding of the biophysical, economic and socialsustainability of UPA systems may also allow us to derive importantconclusions for the farm-level adoption of improved soil fertility managementoptions in the vast rainfed systems across semi-arid Africa and parts of Asia.