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Terracing

Value Chain
Annual Average Rainfall
Soils
Topography
Climatic Zone
Water Source
Altitudinal Zone
Decision Making
Farming Characteristics
Mechanisation
Labour Intensity
Initial Investment
Maintenance Costs
Access to Finance/Credit
Extension Support Required
Access to Inputs
Access to Markets
Gender/Youth Smart
Description

Terraces are cross-slope barriers that have been cut into slopes offering surfaces that are flat or slightly sloped. Terraces are designed to minimise erosion and increase the infiltration of runoff water. In addition, terracing allows for a maximum of area for farming and cropping by cutting into slopes, creating steps on a hillside. Riser walls are retained by growing trees or grasses, using stones or compacted soil to manage runoff and ensure stability. Terracing involves significant planning and labour to implement and maintain. Labour should be coordinated and planned to ensure that terracing is not carried out in an ad hoc manner, and labour to maintain the terraces is available annually. Terracing is suited to areas with severe erosion hazards, deep soils, on slopes that do not exceed 25 degrees and are not too stony. Community action is often required, as terracing is a landscape-level solution that can only be implemented if all parties agree and convert slopes together. Implementing individual terraces or terraced sections can negatively impact the entire hillside.

Technical Application

To effectively approach to terracing construction:

  • Step 1: Measure slope angle – should not exceed 25 degrees and soils should be at least 0.5 metres deep.
  • Step 2: Plot the contours – see Technical Brief 16 Contour Planting for instructions for staking-out contours, and the diagram below for use of a t-stick to measure the distance between contours.
  • Step 3: Start at the lowest terrace. Dig a trench vertically below the next contour, and then dig outwards to the lowest contour. Remove soil and place downhill below the lowest contour.
  • Step 4: Compact soil on constructed terrace.
  • Step 5: Work should then progress upslope, emptying top-soil on to the terrace below to provide soil for planting.
  • Step 6: Strengthen riser buttress walls (back-walls) with stones, compacted soil, or by planting grass or trees.
  • Step 7: Terrace-end drainage should also be considered, so water does not pool too heavily. The down-field gutters can be lined with stones to reduce erosion

Detailed diagrams and tables for calculating terrace dimensions are provided in Peace Corps 1986, Soil conservation techniques for hillside farming.

Additional guidance can be sought from videos provided by Access Agriculture: SLM02 Fanya Juu terraces. The Kenyan example provided is also up-slope terrace construction but using a different method where a trench is dug, and the loose topsoil is thrown up-hill (fanya juu in Kiswahili) which forms a ridge that flattens over time.

Return on Investment Realisation Period
Crop Production
Fodder Production
Farm Income
Household Workload
Food Security
Soil Quality/Cover
Biological Diversity
Flooding
Crop/Livestock Water Availability
Wind Protection
Erosion Control
Increase Production
Stable slopes are a critical element of maintaining agricultural productivity.
Increase Resilience
Terraces enhance slope stability and reduce soil erosion in the face of changing climates, with changing temperature and rainfall regimes.
Additional Information
PDF File
/sites/secondsite/files/tb/CCARDESATechnicalBrief_18_Terracing_2019-10-17_0.pdf
Benefits and Drawbacks

Benefits

  • Terracing prevents erosion and can act as a rainfed irrigation system.
  • Terracing is a labourious process to implement and takes significant effort to maintain.

Drawbacks

  • Requires professional advice on implementing terracing.
  • If implemented incorrectly, can have negative impacts including more erosion than without terracing.

Contour Planting

Value Chain
Annual Average Rainfall
Soils
Climatic Zone
Water Source
Decision Making
Farming Characteristics
Mechanisation
Labour Intensity
Initial Investment
Maintenance Costs
Access to Finance/Credit
Extension Support Required
Access to Inputs
Access to Markets
Gender/Youth Smart
Description

Contour Planting is a planting strategy for sloping fields, where crop rows follow slope contours rather than planting in rows up- and down-slope. The primary aim of this strategy is to slow the downhill flow of water and encourage the infiltration of water into the soil. Slowing the flow of runoff water reduces soil erosion and therefore also nutrient loss.

Contour Ridges are created by tilling, ploughing or hoeing soil to establish ridges along contour lines, acting as a barrier to downhill water runoff and other erosive processes - the higher the ridge height, the more effective the barrier is to preventing soil erosion.

Contour Strips involves use of vegetative barriers e.g. planting of strips of grass or hedges and other species to secure soil and further prevent erosion. These practices are labour intense and require extension support, especially as contour lines are not straight but follow slope characteristics, correctly identifying contour lines is important and can be done using the ‘low-technology’ options that are identified in the Technical Application section of this Technical Brief.

Technical Application

To effectively undertake contour planting:

  • Step 1: Construct an A-frame that has a plumb-line with a rock hanging down the centre. The base of the A-frame should be 90 cm.
  • Step 2: Calibrate the A-frame on flat ground. Ensure that both legs are on the ground. Mark where the plumb line meets the cross bar.
  • Step 3: On a slope, working perpendicular to the slope, plant one leg of the A-frame and swing the other leg around until the plumb line meets the mark on the cross bar. Drive a stake into the ground where the first ‘planted’ leg is and continue the process across the slope.
  • Step 4: Once the extent of the contour has been staked, tie a string from post-to-post across the slope; this identifies the contour to be planted.
  • Step 5: Plant selected crops, develop contour ridges or plant contour strips along the contour line.
  • Step 6: Subsequent contours should be spaced 3-5 m up or downhill of the preceding contour line. To determine the length between contour lines, measure off the top of each stake to a stake up or downhill with a tape measure or accurately measured third stick.
  • Step 7: Contour ridges can be implemented like Water Spreading Bunds (Technical Brief 28) to form ridges of soil that are formed by tilling or ploughing and can be left after land preparation to further prevent erosive forces. Crops can be planted between these ridges.
  • Step 8: The planting of contour strips can be implemented by planting grasses or hedges 20 m (shallow slopes) to 10 m (steeper slopes) apart up or downhill, similar to Trash Lines (Technical Brief 14). This intercropping allows for erosion control and can be used as fodder for livestock.
Return on Investment Realisation Period
Crop Production
Fodder Production
Farm Income
Household Workload
Food Security
Soil Quality/Cover
Biological Diversity
Flooding
Crop/Livestock Water Availability
Wind Protection
Erosion Control
Increase Production
Retaining soil structure enables farmers, particularly those planting on sloping fields to maintain productivity.
Increase Resilience
This land management practice aid farmers to maintain soil structure in the face of changing climates and shifting rainfall patterns.
Additional Information
PDF File
/sites/secondsite/files/tb/CCARDESATechnicalBrief_16_ContourPlanting_2019-10-17_0.pdf
Benefits and Drawbacks

Benefits

  • Contour planting prevents erosion on sloped fields and efficiently trap runoff water.
  • Contour planting improved water infiltration and contour ridges improve water retention.
  • Contour planting can be integrated with intercropping contour strips of grass or hedges to help maintain soil structure.

Drawbacks

  • Contour lines are extremely labour intensive and take a significant amount of time to implement.
  • During contour measuring and development, land may be exposed to erosive forces.
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