A field where the technology is applied, Tonle Sap river in the background. (Christoph Kaufmann (Centre for Development and Environment CDE))

Mulching with water hyacinth (Eichhornia crassipes) after the monsoon floods. (Cambodia)

ការប្រើប្រាស់កំប្លោកជាគម្របដីដំាដំណំាក្រោយពេលទឹកសម្រក (Khmer)

Description

Water hyacinth (Eichhornia crassipes) is collected during the monsoon floods, attached to poles on the flooded fields, chopped when the water recedes and used as mulch to plant different crops.

This mulching technique is used at the riverside of the Tonle Sap River. The area is flooded during the late rainy season (September to November), and alluvial mud is deposed on the fields, which enhances the soil fertility. The deposition of sediments depends on the extent of the yearly flood, and is threatened by the construction of hydropower dams on the upper Mekong River (Thomas et al. 2012:49), as well as climate change (floods tend to be smaller or more extreme). During the dry season (approximately from January to June, depending on precipitation patterns) the land dries and due to high temperatures and very low precipitations, crops can be harmed.

At first, the farmer gathers the water hyacinth with his boat during the wet season. He surrounds them with a net and pulls them to his fields, where he prepares fences with bamboo poles and iron wires. He fills the fenced area with the water hyacinth. Once the water recedes, he sprays glyphosate on the water hyacinths and chops them by using a hand tractor. He plants his first crop, watermelon, as soon as the soil is dry enough (start of dry season). The crop residues of the watermelon are left on the fields, and he can plant a crop of corn and a crop of cucumber before the next flood enters.

The analyzed area is flat (slope < 2%), tropic (dry and wet season), and the soils are mostly loamy. The groundwater table is rather high with 1-2 m during the dry season (November to May). The area is flooded during and after the wet season (August-September to November). The floods bring sludge and thus nutrients to the fields.
Due to climate change, the rainfalls are more erratic, temperatures rise and droughts are more recurrent. Chili is the cash crop predominantly grown in the flooded area, with floating rice as second crop.

Agricultural activity in this region is confronted with high migration rates (garment industry, cities, or other countries). This is detrimental for the farmers, since there is less labour force available. Also, the presented technology requires a rather high initial investment (especially when a tractor is bought) and an increase of physically strenuous labour. Therefore, the interviewed land user stated that most farmers are reluctant to do high investments on their farm. This is aggravated due to the fact that taking up credits might increase the dependency of the farmer.

Location

Location: Kampong Os, Kampong Chhnang, Cambodia

No. of Technology sites analysed:

Geo-reference of selected sites
  • n.a.

Spread of the Technology: evenly spread over an area (0.02 km²)

In a permanently protected area?:

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

Type of introduction
Watermelons are growing on a field covered with mulch. (Christoph Kaufmann (Centre for Development and Environment CDE))

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

  • Cropland
    • Annual cropping: cereals - maize, vegetables - melon, pumpkin, squash or gourd, cucumber
    Number of growing seasons per year: 1
    Is crop rotation practiced? Ja

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

Purpose related to land degradation
  • prevent land degradation
  • reduce land degradation
  • restore/ rehabilitate severely degraded land
  • adapt to land degradation
  • not applicable
Degradation addressed
  • chemical soil deterioration - Cn: fertility decline and reduced organic matter content (not caused by erosion)
  • biological degradation - Bq: quantity/ biomass decline, Bl: loss of soil life
  • water degradation - Ha: aridification
SLM group
  • improved ground/ vegetation cover
SLM measures
  • agronomic measures - A1: Vegetation/ soil cover, A2: Organic matter/ soil fertility, A3: Soil surface treatment

Technical drawing

Technical specifications
Top Right: during the flooded season, water hyacinths are gathered and attached over the fields.
Bottom right: after the floods, the water hyacinths are killed with herbicides (1) and chopped with a hand tractor (2).
Bottom and top left: Different crops follow each other, in this case water melon (3), corn (4) and cucumber (5). The crop residues are always left on the fields.
Kampong Chhnang
Date: 2014

Technical knowledge required for field staff / advisors: moderate
Technical knowledge required for land users: moderate
Main technical functions: improvement of ground cover, increase in organic matter, increase / maintain water stored in soil
Secondary technical functions: control of raindrop splash, improvement of surface structure (crusting, sealing), increase in nutrient availability (supply, recycling,…)

Mulching
Material/ species: Water hyacinths
Quantity/ density: n/a
Remarks: As much as the land user can keep with the bamboo poles and wires.

Minimum tillage
Quantity/ density: n/a
Remarks: Sometimes, the land user tills before the yearly floods due to time issues.
Author: Stefan Graf, Switzerland

Establishment and maintenance: activities, inputs and costs

Calculation of inputs and costs
  • Costs are calculated:
  • Currency used for cost calculation: n.a.
  • Exchange rate (to USD): 1 USD = n.a
  • Average wage cost of hired labour per day: 5.00
Most important factors affecting the costs
The factor affecting the costs the most is the availability of cheap equipment. For the recurrent activities the labour costs were calculated as if he hired someone, but he does all by himself. The work is strenuous, as he has to walk in water and trough the water hyacinths.
Establishment activities
n.a.
Establishment inputs and costs
Specify input Unit Quantity Costs per Unit (n.a.) Total costs per input (n.a.) % of costs borne by land users
Equipment
tools ha 1.0 130.0 130.0 100.0
boat ha 1.0 1000.0 1000.0 100.0
hand tractor ha 1.0 1500.0 1500.0 100.0
Fertilizers and biocides
biocides ha 1.0 4.5 4.5 100.0
Construction material
wires and bamboo poles ha 1.0 30.0 30.0 100.0
Total costs for establishment of the Technology 2'664.5
Total costs for establishment of the Technology in USD 2'664.5
Maintenance activities
  1. Collecting water hyacinth and put poles (Timing/ frequency: During the floods each year (Oct-Nov))
  2. Spraying herbicide on the water hyacinth (Timing/ frequency: After floods)
  3. Chopping the sprayed water hyacinth with the hand tractor (Timing/ frequency: After spraying herbicide)
Maintenance inputs and costs
Specify input Unit Quantity Costs per Unit (n.a.) Total costs per input (n.a.) % of costs borne by land users
Labour
labour ha 1.0 35.0 35.0 100.0
Equipment
machine use ha 1.0 10.0 10.0 100.0
Total costs for maintenance of the Technology 45.0
Total costs for maintenance of the Technology in USD 45.0

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
Thermal climate class: tropics. 27-35°C
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
Water quality refers to:
Is salinity a problem?
  • Ja
  • Nee

Occurrence of flooding
  • Ja
  • Nee
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: 50
Quantity after SLM: 100
According to the farmer the yield doubled.

product diversity
decreased
increased


Grows other cash crops than the other farmers in the area.

demand for irrigation water
increased
decreased

expenses on agricultural inputs
increased
decreased

workload
increased
decreased


However, there is less irrigation work needed.

Socio-cultural impacts
conflict mitigation
worsened
improved

Ecological impacts
water quality
decreased
increased


Herbicide is used in the river.

evaporation
increased
decreased

soil moisture
decreased
increased

soil cover
reduced
improved

nutrient cycling/ recharge
decreased
increased

soil organic matter/ below ground C
decreased
increased

pest/ disease control
decreased
increased


Problems with insects

Off-site impacts
groundwater/ river pollution
increased
reduced


Herbicide goes into the river

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

A hand tractor could be rented instead of bought

Climate change

Gradual climate change
annual temperature increase

not well at all
very well
Climate-related extremes (disasters)
local rainstorm

not well at all
very well
local windstorm

not well at all
very well
drought

not well at all
very well
general (river) flood

not well at all
very well
Other climate-related consequences
reduced growing period

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%
  • 11-50%
  • > 50%
Of all those who have adopted the Technology, how many have done so without receiving material incentives?
  • 0-10%
  • 11-50%
  • 51-90%
  • 91-100%
Has the Technology been modified recently to adapt to changing conditions?
  • Ja
  • Nee
To which changing conditions?
  • climatic change/ extremes
  • changing markets
  • labour availability (e.g. due to migration)

Conclusions and lessons learnt

Strengths: land user's view
  • It is easy to keep the water hyacinth on the fields after the floods
  • The soil keeps the water, less loss due to evaporation. He uses less water for irrigation
  • The plants grow better and have higher yields
Strengths: compiler’s or other key resource person’s view
  • The soil is covered, so it needs less irrigation.
  • The land user needs less fertilizer as the soil fertility, biological activity and carbon content is higher.
Weaknesses/ disadvantages/ risks: land user's viewhow to overcome
  • The profit is not in relation to the work. Plant more profitable cash crops; share the machines with other farmers.
  • The soil is too wet after the floods because the mulch stops the evaporation. Grow a water loving plant as first cash crop.
  • Only physically strong people can do the work. Build simplified water hyacinth harvesting structures.
Weaknesses/ disadvantages/ risks: compiler’s or other key resource person’s viewhow to overcome
  • Herbicides are used in an aquatic environment. Find a chopping device that is sufficient to kill the water hyacinth on its own.
  • The initial investments are high. Tractor bank could be implemented (share the cost of the machines amongst members.)

References

Compiler
  • Christoph Kaufmann
Editors
Reviewer
  • Deborah Niggli
  • Alexandra Gavilano
Date of documentation: Okt. 16, 2014
Last update: Sept. 2, 2019
Resource persons
Full description in the WOCAT database
Linked SLM data
Documentation was faciliated by
Institution Project
Key references
  • Thomas, T.S., Ponlok, T., Bansok, R., et al. 2012. Cambodian Agriculture: Adaptation to Climate Change Impacts. A Report for USAID.: cgiar.org; free
This work is licensed under Creative Commons Attribution-NonCommercial-ShareaAlike 4.0 International