Grevillea Robusta provides shade to the pineapple fruits grown, dead leaves decompose to soil organic matter which makes the garden fertile. (Betty Adoch)

Grevillea Robusta (Silk Oak) Boundary Lines on a Pineapple Cropland (Uganda)

Yen ipoto

Description

Leguminous, fast growing grevillea robusta (silk oak) planted as boundary lines provides shade to a pineapple cropland, increases soil organic matter, provides fuel wood for domestic use and timber for construction after 5-8 years.

Grevillea Robusta (silk oak) is a leguminous, fast growing and evergreen tree planted in a natural environment with tropical savanna climate of Northern Uganda which receives rainfall of about 750-1000 mm per annum, established on a generally flat slope with an altitude of about 1000 meters above sea level. The soil type is moderately fertile with low moisture content that favours tree growth. These trees are planted as boundary lines for providing shade on a pineapple cropland, nitrogen fixation, increasing soil organic matter, providing fuel wood and as a source of timber for construction after 5-8 years. The tree species generally grows well under the mono-modal (one rainfall season) rainfall pattern of Northern Uganda.

Planting is normally done during the wet season at the onset of rain in early April and the inputs required for establishing this technology include Grevillea Robusta seedlings majorly provided by the District forestry officers, farmyard manure, hand hoes and spades. A hand hoe is used to dig pits about 0.5 m deep, 0.6 m wide and 3 to 5 m apart and 1 meter away from the pineapple crop. Farmyard manure is added to the pit to fill a depth of about 0.3 m, a layer of top soil is added to 0.2 m depth and the seedling is planted on top. The rest of the pit is filled with soil and watered to improve soil moisture content. Bamboo canes can be woven around the seedlings to protect them from destruction by livestock. Grevillea Robusta grows fast when the boundary line is well established within two years. The pruned branches provide fuel wood for domestic use like cooking and within 5 to 8 years the trees are harvested for timber. Establishment costs for this technology are normally higher compared to maintenance costs especially for the purchase of Grevillea seedlings, manures, farm equipment like hand hoes and pangas. The technology is easily and spontaneously adopted by average smallholder farmers with less than 2 acres and is useful for providing shade to the pineapple crop thus increasing the yield. What is not liked about this technology is that it forms a big canopy that limits photosynthesis. To maintain this technology, the land user has to constantly prune whenever the canopy grows big.

Location

Location: Pader Town Council, Northern Uganda., Uganda

No. of Technology sites analysed: single site

Geo-reference of selected sites
  • 32.9923, 3.00843

Spread of the Technology: evenly spread over an area (approx. < 0.1 km2 (10 ha))

Date of implementation: 2012; less than 10 years ago (recently)

Type of introduction
Grevillea trees along the pineapple crop field (Betty Adoch.)

Classification of the Technology

Main purpose
  • improve production
  • reduce, prevent, restore land degradation
  • conserve ecosystem
  • protect a watershed/ downstream areas – in combination with other Technologies
  • preserve/ improve biodiversity
  • reduce risk of disasters
  • adapt to climate change/ extremes and its impacts
  • mitigate climate change and its impacts
  • create beneficial economic impact
  • create beneficial social impact
Land use

  • Mixed (crops/ grazing/ trees), incl. agroforestry - Agroforestry
    Main products/ services: Grevillea trees act as windbreak, provide shade and increase soil organic matter for pineapple crops.

Water supply
  • rainfed
  • mixed rainfed-irrigated
  • full irrigation

Number of growing seasons per year: 1
Land use before implementation of the Technology: The land was used for growing vegetables.
Livestock density: n.a.

Purpose related to land degradation
  • prevent land degradation
  • reduce land degradation
  • restore/ rehabilitate severely degraded land
  • adapt to land degradation
  • not applicable
Degradation addressed
  • soil erosion by wind - Et: loss of topsoil, Ed: deflation and deposition
SLM group
  • agroforestry
  • windbreak/ shelterbelt
  • integrated soil fertility management
SLM measures
  • agronomic measures - A5: Seed management, improved varieties
  • vegetative measures - V1: Tree and shrub cover

Technical drawing

Technical specifications
Author: Betty Adoch.
A hole is dug at a depth of 0.5 m, and 0.6 m wide. Farm yard manure added into the hole at a depth of 0.3 m and soil added to 0.2 m depth to fill up the hole in which tree seedlings are planted at a spacing of 3 or 5 meters apart since they do not form a huge canopy and 1 meter away from the pineapple crop.

Establishment and maintenance: activities, inputs and costs

Calculation of inputs and costs
  • Costs are calculated: per Technology area (size and area unit: 7 acres)
  • Currency used for cost calculation: UGX
  • Exchange rate (to USD): 1 USD = n.a UGX
  • Average wage cost of hired labour per day: 3,000 shs
Most important factors affecting the costs
The Grevillea seedlings were distributed at a cost from the District. There is also high cost of hiring labour. However, family members can also help in maintaining the technology.
Establishment activities
  1. Land clearing (Timing/ frequency: Late March)
  2. Procurement of seedlings (Timing/ frequency: March)
  3. Planting (Timing/ frequency: Early April at onset of rainfall)
  4. Weeding (Timing/ frequency: May during wet season)
  5. Pruning (Timing/ frequency: November in wet season)
  6. Harvesting (Timing/ frequency: December during dry season for timber)
Establishment inputs and costs (per 7 acres)
Specify input Unit Quantity Costs per Unit (UGX) Total costs per input (UGX) % of costs borne by land users
Labour
Hired labour Day 30.0 3000.0 90000.0 100.0
Equipment
Hoe pieces 10.0 12000.0 120000.0 100.0
Panga pieces 5.0 10000.0 50000.0 100.0
Plant material
Grevillea seedlings pieces 500.0 100.0 50000.0 100.0
Fertilizers and biocides
Manure Kgs 20.0 5000.0 100000.0 100.0
Construction material
Bamboo reeds pieces 100.0 1000.0 100000.0 100.0
Total costs for establishment of the Technology 510'000.0
Maintenance activities
  1. Pruning (Timing/ frequency: November)
  2. Weeding (Timing/ frequency: May)
Maintenance inputs and costs (per 7 acres)
Specify input Unit Quantity Costs per Unit (UGX) Total costs per input (UGX) % of costs borne by land users
Labour
hired labour days 5.0 3000.0 15000.0 100.0
Equipment
hoes pieces 10.0 12000.0 120000.0 100.0
pangas pieces 5.0 10000.0 50000.0 100.0
Total costs for maintenance of the Technology 185'000.0

Natural environment

Average annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Agro-climatic zone
  • humid
  • sub-humid
  • semi-arid
  • arid
Specifications on climate
Average annual rainfall in mm: 1000.0
Moderate rain from April to October which supports the growth of the trees.
Name of the meteorological station: kitgum weather station
Tropical savanna climate
Slope
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
Landforms
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitude
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.
Technology is applied in
  • convex situations
  • concave situations
  • not relevant
Soil depth
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil)
  • coarse/ light (sandy)
  • medium (loamy, silty)
  • fine/ heavy (clay)
Soil texture (> 20 cm below surface)
  • coarse/ light (sandy)
  • medium (loamy, silty)
  • fine/ heavy (clay)
Topsoil organic matter content
  • high (>3%)
  • medium (1-3%)
  • low (<1%)
Groundwater table
  • on surface
  • < 5 m
  • 5-50 m
  • > 50 m
Availability of surface water
  • excess
  • good
  • medium
  • poor/ none
Water quality (untreated)
  • good drinking water
  • poor drinking water (treatment required)
  • for agricultural use only (irrigation)
  • unusable
Is salinity a problem?
  • Yes
  • No

Occurrence of flooding
  • Yes
  • No
Species diversity
  • high
  • medium
  • low
Habitat diversity
  • high
  • medium
  • low

Characteristics of land users applying the Technology

Market orientation
  • subsistence (self-supply)
  • mixed (subsistence/ commercial
  • commercial/ market
Off-farm income
  • less than 10% of all income
  • 10-50% of all income
  • > 50% of all income
Relative level of wealth
  • very poor
  • poor
  • average
  • rich
  • very rich
Level of mechanization
  • manual work
  • animal traction
  • mechanized/ motorized
Sedentary or nomadic
  • Sedentary
  • Semi-nomadic
  • Nomadic
Individuals or groups
  • individual/ household
  • groups/ community
  • cooperative
  • employee (company, government)
Gender
  • women
  • men
Age
  • children
  • youth
  • middle-aged
  • elderly
Area used per household
  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Scale
  • small-scale
  • medium-scale
  • large-scale
Land ownership
  • state
  • company
  • communal/ village
  • group
  • individual, not titled
  • individual, titled
Land use rights
  • open access (unorganized)
  • communal (organized)
  • leased
  • individual
Water use rights
  • open access (unorganized)
  • communal (organized)
  • leased
  • individual
Access to services and infrastructure
health

poor
good
education

poor
good
technical assistance

poor
good
employment (e.g. off-farm)

poor
good
markets

poor
good
energy

poor
good
roads and transport

poor
good
drinking water and sanitation

poor
good
financial services

poor
good

Impacts

Socio-economic impacts
Crop production
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

wood production
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

land management
hindered
simplified

Quantity before SLM: low
Quantity after SLM: high

energy generation (e.g. hydro, bio)
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

farm income
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

diversity of income sources
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

Socio-cultural impacts
SLM/ land degradation knowledge
reduced
improved

Quantity before SLM: low
Quantity after SLM: high

Ecological impacts
soil moisture
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

soil cover
reduced
improved

Quantity before SLM: low
Quantity after SLM: high

soil loss
increased
decreased

Quantity before SLM: high
Quantity after SLM: low
the trees protect the soil from erosion

soil organic matter/ below ground C
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

vegetation cover
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

biomass/ above ground C
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

plant diversity
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

beneficial species (predators, earthworms, pollinators)
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

habitat diversity
decreased
increased

Quantity before SLM: low
Quantity after SLM: high

wind velocity
increased
decreased

Quantity before SLM: high
Quantity after SLM: low
trees protect the pineapple garden from strong wind

Off-site impacts
buffering/ filtering capacity (by soil, vegetation, wetlands)
reduced
improved

Quantity before SLM: Low
Quantity after SLM: High
Grevillea trees act as windbreak on a pineapple field

Cost-benefit analysis

Benefits compared with establishment costs
Short-term returns
very negative
very positive

Long-term returns
very negative
very positive

Benefits compared with maintenance costs
Short-term returns
very negative
very positive

Long-term returns
very negative
very positive

Climate change

Gradual climate change
annual temperature increase

not well at all
very well
seasonal temperature increase

not well at all
very well
Season: wet/ rainy season
annual rainfall decrease

not well at all
very well
seasonal rainfall decrease

not well at all
very well
Season: wet/ rainy season
Climate-related extremes (disasters)
local rainstorm

not well at all
very well
local thunderstorm

not well at all
very well
local hailstorm

not well at all
very well
drought

not well at all
very well
forest fire

not well at all
very well

Adoption and adaptation

Percentage of land users in the area who have adopted the Technology
  • single cases/ experimental
  • 1-10%
  • 10-50%
  • more than 50%
Of all those who have adopted the Technology, how many have done so without receiving material incentives?
  • 0-10%
  • 10-50%
  • 50-90%
  • 90-100%
Has the Technology been modified recently to adapt to changing conditions?
  • Yes
  • No
To which changing conditions?
  • climatic change/ extremes
  • changing markets
  • labour availability (e.g. due to migration)
The grevillea robusta trees increase soil water retention after heavy rainfall episodes, and organic matter.

Conclusions and lessons learnt

Strengths: land user's view
  • Grevillea trees when mature provide timber for construction.
  • Grevillea tree branches when pruned supply fuel wood.
  • The dry tree leaves decompose and provide manure for the garden.
Strengths: compiler’s or other key resource person’s view
  • Grevillea robusta provides many soil conservation benefits like nitrogen fixing and soil moisture retention among them.
  • Young shoots from grevillea robusta provide animal fodder.
  • The trees helps modify the microclimate.
Weaknesses/ disadvantages/ risks: land user's viewhow to overcome
  • Trees take up some of the cropland that should have been used to grow other crops. Agroforestry
  • Labour intensive in terms of pruning trees. Family members to provide labour
Weaknesses/ disadvantages/ risks: compiler’s or other key resource person’s viewhow to overcome
  • Grevillea provides shade to pineapple crops that obstructs the photosynthesis process. Plant grevillea at a distance from the plant

References

Compiler
  • betty adoch
Editors
  • Kamugisha Rick Nelson
  • Bernard Fungo
Reviewer
  • John Stephen Tenywa
  • Nicole Harari
  • Renate Fleiner
Date of documentation: June 7, 2017
Last update: July 16, 2019
Resource persons
Full description in the WOCAT database
Linked SLM data
Documentation was faciliated by
Institution Project
Links to relevant information which is available online
This work is licensed under Creative Commons Attribution-NonCommercial-ShareaAlike 4.0 International