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Weed Control

Value Chain
Climatic 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

Weeds are any unwanted plant species that compete with crops for sunlight, water, nutrients, air and space, hindering crop growth and in some cases are even toxic to crop plants. Weed control measures can be applied in an integrated manner to help prevent the growth and spread of weeds in agricultural systems. An integrated weed management approach aims to restrict weed growth until a crop is well established and can outcompete weeds. This integrated approach includes biological, chemical, cultural and/or physical tactics to combat weed spread and growth and these practices can be more cost effective than herbicide applications. Integrated weed management is climate smart as it combines multiple climate smart practices that increase farmers resilience, limits GHG releases and increases productivity. Options for weed control include crop rotation, intercropping, cover crops (which can be used as green manure or mulch), mulching, seed-bed preparation, livestock grazing, seed/variety selection, mowing, and hand-weeding.

The application of integrated weed control is climate smart as it reduces herbicide application and reduction in machinery usage (i.e. through no-tillage practices).

Technical Application

To effectively undertake weed control measures:

  • Step 1: Review weed control measures - crop rotation, intercropping, cover crops, mulching, seed-bed preparation, livestock grazing, seed/variety selection, mowing, hand-weeding and adjustments to tillage practices - and determine which methods are available and appropriate for the farming system and farmer. Two or more of these techniques can be applied to assist in ensuring farmers have more chance of success. Understand possible negative impacts of each weed control method.
  • Step 2: Improve weed identification knowledge in specific areas.
  • Step 3: Prevent weeds from spreading – clean clothes, animals, machinery, vehicles to limit weed transport; use only well stored/rotted manure (4-5 months) (Knowledge Product 16), include fencing, irrigation and other farm ‘breaks’ where possible
  • Step 4: Apply a combination of weed control methods including – cover crops (Technical Brief 15), mulching, intercropping (Technical Brief 07), crop rotation (Technical Brief 09), livestock grazing, seed selection (Technical Brief 20), mowing, hand-weeding. Try to avoid the application of herbicides, tillage and burning.
  • Step 5: monitor and document most effective weed management strategies for each farmer, and use lessons learned from the area with other farmers where applicable.
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
Weed control supports agricultural productivity by removing competition while reducing the need for herbicides.
Additional Information
PDF File
/sites/secondsite/files/tb/CCARDESATechnicalBrief_19_WeedControl_2019-10-17_0.pdf
Benefits and Drawbacks

Benefits

  • Integrated weed management involves employing two or more climate smart practices.
  • Reduced consumption of chemicals
  • Cost effective methods that do not require additional inputs.

Drawbacks

  • More time consuming than applying herbicides or other more destructive methods.
  • Strategy requires careful planning.
  • May not be 100% effective.

Lime Treatment of Soil

Value Chain
Soils
Climatic 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

Soil acidification is a widespread problem across southern Africa, often driven by monocropping with cereals and occurring as a result of erosion, compost decomposition and soil leaching. Applying lime to soil is regarded as a key management practice in agriculture to balance pH, enhancing crop productivity, water penetration and absorption of major nutrients by crops. Most crops grow best in soils with a pH between 6.5 and 6.8. Acidity constrains crop growth below pH levels of 5.5. Agricultural lime is limestone mined as a rock that is crushed into various particle sizes ranging from course to fine particles and can be applied in areas where there is high soil-acidity due to high levels of manganese and iron. Lime texture also determines the speed of absorption in the soil; that is, fine-lime reacts more quickly than more granular lime. However, the use of lime must be managed appropriately to avoid losing other nutrients in the soil. This practice is considered climate smart as it assists with adaptation strategies through improvement of soil fertility, whilst improving productivity at modest application rates, noting that annual application is not recommended.

Technical Application

Before applying lime to increase lower soil pH the following should be considered. Equipment required: soil pH testing kit, protective goggles and mask, agricultural lime, shovels/forks/hoes, and disk harrow, drag harrow or hoe if available.

  • Step 1: Use a pH testing strip to determine soil pH levels, making sure to test surface and sub-surface acidity.
  • Step 2: Measure area of land to be treated in order to determine amount of lime for purchase. Application should be calculated as metric tonne per hectare, depending on soil pH and crop. Lime requirements will differ depending on soil type and level of acidity in the soil. Application volumes can be guided by suppliers.
  • Step 3: Purchase lime according to requirements from agricultural supplier. Savings could be realised if purchasing as a group of farmers.
  • Step 4: Apply lime to the soils at least two months prior to planting directly after harvesting to allow the lime to react with the soil, and positively impact the pH.
  • Step 5: Mix lime and soil well in order to reduce soil acidity. This is normally achieved through disk tilling but can be done manually using a drag harrow or hoe. However, this can be an intensive process.
  • Step 6: Test pH prior to planting to ensure amendments have improved soil pH.
  • Step 7: Plant crops. Monitor crop performance, and harvest results with a view to understanding impact of lime treatment.
  • Step 8: Following harvest, test soil pH again.

Application of lime can be part of an Integrated Soil Fertility Management (ISFM) practices.

While a practical solution, this soil amendment should be informed by research and discussion with extension officers and lime suppliers. On-farm storage and management of lime should be included in this dialogue.

Return on Investment Realisation Period
Crop Production
Fodder Production
Farm Income
Household Workload
Food Security
Soil Quality/Cover
Biological Diversity
Crop/Livestock Water Availability
Wind Protection
Erosion Control
Increase Production
Significant increases in productivity.
Increase Resilience
Sustainable improvements to soil fertility. Application is not required every year.
Additional Information
PDF File
/sites/secondsite/files/tb/CCARDESATechnicalBrief_05_AddingLime_2019-10-17_0.pdf
Benefits and Drawbacks

Benefits

  • Lime treatment can assist farmers to balance pH in acidic soils, optimising water and nutrient use for crop plant growth.
  • A practical and effective way to combat the negative effects of erosion, compost decomposition and leaching on soil.
  • Lime does not need to applied to soil every year.

Drawbacks

  • Adding lime to soils is laborious and should not be considered a short-term solution to balancing soil pH.
  • Over-application or overuse of lime can negatively affect soil quality.
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Beneficiaries Reached

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Farmers Trained

3720

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41300

Lead Farmers Supported