Tree – Vegetable Interaction in
Vegetable Agroforestry
Systems
Progress Report
Agustin R. Mercado, Jr
ICRAF
TMPEGS
•Technology:
–Develop economically viable
and ecologically-sound
vegetable-agroforestry (VAF)
systems
Overall hypothesis
In intensive vegetable production
system in the uplands, monoculture
systems are not sustainable, but
integrating trees is feasible and
offers better prospects.
Vegetable Agroforestry System (VAF)
Research goal:
Tree-vegetable integration on farm
with minimal negative interaction,
thus increasing productivity,
economic profitability, nutrient use
efficiency and environmental
services
VAF Research Issues
•
•
•
AF systems
– Segregate
– Integrate
• Boundary planting
• Parklands
• Alleycropping or hedgerow intercropping
Tree species
– Timber trees
– Fruit trees
– Canopy type: broad, medium, narrow
Vegetable types
– Crucifers: Cabbages, Broccoli, Squash
– Tubers: Potato,
– Solanaceous: Tomato, eggplant,
Specific hypotheses
• Vegetable based agroforestry (VAF) systems
provide better productivity, increase fertilizer
use efficiency (FUE), increase profitability and
improve environmental services than vegetable
monoculture system
• Application of model allows a more rapid
progress in on-farm trials and site-management
designs
• Integration (domestication) of indigenous tree
vegetables offers additional option for
sustained supply of vegetables for poor rural
households.
Two research topics:
1. VAF tree-soil-crop interaction
2. Domestication of indigenous tree
vegetables
General objectives
• To understand the nature of vegetable-soil-tree
interactions in different types of tree integration on
vegetable systems as the determinant for agrosilvocultural management options for enhancing the
productivity of all components ( tree, vegetable, etc).
• To examine service functions provided by VAF
systems such as nutrient safety-net and nutrient pump
functions, carbon stocks (above-and belowground) and
build up of soil organic matter (SOM)
Specific objectives
• To determine existing VAF systems and understand its potential and
constraints
• To evaluate existing VAF systems on light capture and tree growth and
spatial vegetable productivity in relation to tree distance.
• To improve VAF systems by understanding vegetable –soil – tree
interaction and employing appropriate agro-silvocultural practices in
order to attain optimum productivity of all components.
• To test the hypothesis that tree roots act as safety-net for leached
nutrients in intensive vegetable production system
• To collect and evaluate indigenous tree vegetables under farmers
management
Ongoing and planned research activities
1. Vegetable farming system diagnosis (VFSD)
2. Assessment of existing vegetable based agroforestry
systems.
3. VAF system improvement.
• Optimum light transmission as basis for silvicultural
management (spacing, thinning, pruning, etc).
• Vegetable and tree growth and productivity.
• Tree-vegetable matching
4. Testing the hypothesis that tree roots act as safetynets. Increased fertilizer use efficiency and reduction of
fertilizer leaching (particularly on nitrate) thus avoiding
contamination to water sources. (If 15N enriched fertilizer is
available).
5. Testing the hypothesis that trees act as nutrient pump. Use
of depth placement of 15N method. (If 15N isotope enriched
fertilizer is available).
6. Quantification of environmental services (C
sequestration – contribution of trees to soil organic matter
build up (use of 13C method) and aboveground C stocks.
Develop tree growth and allometric models)
Deliverables
1. Recommendation for vegetable- tree combination and
management with minimal negative interaction
2. Improved options for tree spacing and vegetable-tree
intercrop patterns
3. Profitable vegetable-tree systems identified
Schematic diagram of tree-crop interaction in hedgerow intercropping system
N 2 - fixation
C0 2 - fixation
Net benefit = 2T+ (Y2-2Y1)-2D
where:
T
= value of tree products (inc
above and below C stocks, N2
fixation)
Y1 = yield loss
Y2 = yield gain
D = value of displaced crop
reduction of negative effects through
silvicultural management
Y2
+
Y1
Y1
D
tree-crop nutrient transfer through pruning
and roots and nodules turn-over.
+
uptake from safety- net zone
(nutrient pumping below root
zone of annual crops)
-
leaching of nutrients to lower depths
Safety-net zone
+
=
fertility, micro-climae, erosion control, nutrient pumping, safetynet, tree biomass and soil C stocks
-
=
competition: light, water nutrient
Yield of control
(monocropping
systems)
0 - 100 cm depth
> 100 cm depth
Schematic diagram of tree-crop interaction under parkland system
N 2 - fixation
C0 2 - fixation
Scenario 1. Competition
- Tree is competitive
Net benefit= T+ (2y2-2y1)-D
+
-
D
0 - 100 cm depth
> 100 cm depth
leaching of nutrient
+
uptake of H20, nutrients
Scenario 2. Complementary
+
+
Net benefit = T + (Y2 - D)
Schematic diagram of tree-crop interaction under boundary planting system
Y = T + (Y2 - Y1) - D
+ Y2
Y1
0 - 100 cm depth
> 100 cm depth
D
-
Activities conducted so far:
•
Assessment of existing VAF systems covering 21 farms, 2 AF systems, 6
tree species, 8 vegetables, 4 aspects. Data collected were tree parameters
(stem diameter, tree height, canopy height and width), spatial performance
of vegetables (height, stem diameter, crown width, biomass), spatial light
transmission (fish eye photography/quantum light meter)
•
Focus group discussion with 15 VAF farmers on various ways of integrating
trees on vegetable farms and their practices and experiences on tree and
vegetable managements addressing tree-vegetable competition and
complementarity.
•
Nursery establishment and management of indigenous tree vegetables and
medicinal trees. ,
Eucalyptus robusta + tomato at Gunayan’s farm at Bul-ogan,
Sungco, Lantapan.
Eucalyptus- tomato interaction under boundary planting system
Tomato height
height (cm)
150
140
130
120
110
100
90
80
70
60
50
40
30
Competition
Complementarity
Neutral
20
10
0
0
D
3
6
9
Distance from the tree
12
15
Three zones of tree-crop interaction in vegetable agroforestry systems
White bean yield under Maesopsis eminii hedge trees
20
Competition zone
Complementarity zone
Nuetral zone
Beans (g/plt)
15
10
5
0
0
M. eminii hedge
5
10
Distance from the tree
15
20
\
• Effect was due to:
- Light competition (aboveground)
- Nutrient competition
Effects were due to:
Aboveround (light competition)
Belowground (water, nutrients, etc)
Proportion of total light transmitted spatially using fish-eye
photography analyzed with gap light analyzer software. Farmer
removed approximately 40% of the canopy
Maesopsis em ini +w hite beans
% light transmitted (mols m2-1 d-1)
120
100
80
y = 7.6748Ln(x) + 76.046
R2 = 0.9125
60
40
20
0
0
5
10
Distance from tree (m)
15
20
Net complementarity as a simple tool in assessing
appropriate tree-vegetable integration
• Net complementarity = degree of complementarity-degree of
competitiveness
• Degree of complementarity = relative yield (at complementarity
zone) – 1 x distance of influence
• Degree of competitiveness = 1- relative yield (at competition
zone) x distance of influence
• Relative yield at complementarity zone = yield at complementarity
zone/neutral zone
• Relative yield at competition zone = yield at competition
zone/neutral zone
Three zones of tree-vegetable interaction in vegetable agroforestry
systems
White bean yield under Maesopsis eminii hedge trees
20
Competition zone
Complementarity zone
Nuetral zone
Beans (g/plt)
15
10
5
0
0
M. eminii hedge
5
10
Distance from the tree
15
20
Influence of timber tree species on net
complementarity
Tree species
Net complementarity
n
Acacia mangium
-0.23
1
Eucalyptus robusta
0.48
7
Eucalyptus torillana
-0.30
3
Gmelina arborea
-0.85
8
Maesopsis emini
-1.67
1
Influence of vegetable crops on
net complementarity
Vegetables
Net complementarity
n
Bell pepper
0.14
3
Brocolli
-7.54
1
Cabbage
0.98
2
Cauliflower
0.44
2
Chinese cabbage
0.57
7
Tomato
-0.48
4
White beans
-1.67
1
Maize
-1.55
1
Influence of aspects on net
complementarity
Aspects
Net complementarity
n
East (vegetables on west side)
-1.74
7
West (vegetable on east side)
-1.06
4
North (vegetable on south side)
-0.54
3
South (vegetable on north side)
-2.09
4
Relationship between tree height (m) and
net complementarity
20
y = 0.3034x + 12.696
R2 = 0.14
18
16
Tree height (m)
14
12
10
8
6
4
2
0
(10.00)
(5.00)
-
5.00
Net complementarity
10.00
Relationship between proportion of canopy left
vs net complementarity
Proportion of canopy left (%)
120
y = 2.0991x + 62.359
100
2
R = 0.03
80
60
40
20
0
(10.00)
(5.00)
Net complementarity
5.00
10.00
Relationship between canopy width and net
complementarity
900
800
Canopy width (cm)
700
600
500
y = -14.254x + 560.37
R 2 = 0.08
400
300
200
100
0
(10.00)
(5.00)
Net complementarity
5.00
10.00
Tree spacing vs net complementarity
6
y = 0.1164x + 3.5417
R2 = 0.08
Tree spacing (m)
5
4
3
2
1
0
(10.00)
(8.00)
(6.00)
(4.00)
(2.00)
Net complementarity
-
2.00
4.00
Domestication of indigenous tree vegetables
•
Objectives:
- Collect and propagate indigenous tree vegetables
- Household food and nutritional security (available 365 days a year)
- Environment friendly (no pesticides, better carbon sequestration)
- Seed banking (in situ)
- Reduced production risks
•
Indigenous tree vegetable species:
– Gnetum gnemon – “Bago”
– Abelmuchos manihot – “Lagikway”
– Sesbania sesban – “ Katuray”
– Moringa oliefera – “Malunggay”
– Looking for more entries
 Evaluation activities:
- Propagation methods (clonal propagation and nursery establishment at
Claveria)
- As contour hedgerows
- As live fences
• Medicinal trees
–
–
–
–
–
Cinnamomum mindanensi (Kalingag)
Cinchona pubescens (Kenina)
Camella sinensis (Tea)
Cinnamomum verum (Cinnamon)
Vitex negundo (Lagundi)
• Evaluation activities:
- Clonal propagation methods
- As hedgerows (farmers –managed) as SPA
- As live fence (farmers –managed) as SPA
• Progress so far
– Clonal chamber has been established
– Potted seedlings of 1000 pcs for each of the species have been
raised
– Collection of more entries
Summary and initial findings
1.
Integration of trees on farm is only feasible if :
•
Complementarity is greater than competition (Net complementarity is > 0). Net complementarity
can be a simple tool for assessing appropriate tree-vegetable integration.
•
The cumulative value of tree products is greater than the cumulative values of yield loss and crop
displacement area (cropped area loss).
2. Optimum tree spacing or tree line (hedge spacing) in AF system can be achieved when
two complementarity zones meet. Approximately 25-30 meters apart.
3. Eucalyptus robusta, Eucalyptus torillana and Acacia mangium are promising trees for
VAF system
4. Cabbage, Chinese cabbage, cualiflower and bell pepper are suitable vegetables for
VAF
Thank you very much indeed for
listening!!