Soil fertility is one of the most critical factors needs to be maintained so farmers can continue to grow productive and nutritious crops, especially in southern Africa where soils are often fragile and lacking in plant nutrients. Soils are often quickly depleted if mismanaged, further exacerbated by natural biophysical processes such as rain, wind and/or heat. The use of organic fertiliser can help farmers to improve soil fertility, as they improve absorption of water and add nutrients into the soil, drastically improving crop production. Organic fertilisers are plant (crop residues) or animal-based materials, such as green manure, worm mouldings, compost, animal waste, and sewage residues, many of which may be readily available on the farm, or within a farming community. These products are potential counters to inorganic fertilisers - artificially manufactured chemicals (synthetic) mined from mineral deposits comprising minerals such as nitrogen, phosphorus and magnesium - which are often costly when few farmers can access credit needed to sustainably access such materials. Organic fertilisers are considered climate smart as they utilise (recycle) readily available organic materials to feed soil and crops simultaneously as they add nutrients into the soil and condition it, and thus increase productivity and resilience, while inorganic fertilisers add nutrients to the soil only, and are often expensive.
Organic fertilisers can be produced at the household level or purchased. On-farm production includes stock-piling animal manure, crop residues, and other organic waste, following appropriate guidance for processing and usage.
To apply organic fertilisers the following should be considered:
- Step 1: Assess field area where fertiliser is to be applied, and fertiliser needs – poor crop performance, low organic matter content, etc.
- Step 2: Ensure that fertiliser is available in sufficient quantities for application in all target or priority fields.
- Step 3: Ensure organic fertiliser – especially green manure/crop residues – are broken-down/chopped to aid breakdown/integration with soil.
- Step 4: Monitor soil nutrient levels and crop performance (in the light of prevailing climatic conditions) to determine success of organic fertilisers.
- Chianu, Jonas & Chianu, Justina & Mairura, Franklin. (2012). Organic Fertilizers in Sub-Saharan Farming Systems. 10.1007/978-94-007-4113-3_3.
- Odhiambo, Jude & N. Magandini, Vidah. (2008). An assessment of the use of mineral and organic fertilizers by smallholder farmers in Vhembe district, Limpopo province, South Africa. African Journal of Agricultural Research. 3. 357-362.
- Svotwa, E, R. Baipai and J. Jiyane 2009. Organic Farming in the smaller holder farming sector of Zimbabwe. Journal of Organic Systems Vol 4. No. 1.
Benefits
- Fertilisers can help restore soil nutrients, improve soil conditions and improve crop production if applied correctly.
- Organic fertilisers are plant or animal materials that can be produced locally or purchased for application.
- An appropriate strategy in rural and low-income communities with small holder farmers that can generally not afford synthetic pesticides and inorganic fertilisers.
- Collective action can minimise the financial cost of implementing organic fertilisers, in terms of shared transportation and storage costs, as well as bulk purchasing power.
- Use of organic fertilisers can help avoids the leaching of inorganic fertilisers into waterways, which can result in eutrophication.
- Where farmers do have access to financial resources and/or credit, organic fertilisers should be used in combinate with inorganic application.
Drawbacks
- Manure and other types of organic fertilisers require management, and relevant storage mechanisms. If not stored correctly, investment can be lost as nutrients can be lost due to exposure to the elements.
- It can be costly to transport if sourcing from off-farm
- Weed seeds can be present in manure, increasing labour requirements for weeding.
- If not produced on-farm, organic fertilisers, while beneficial can require access to sustainable financial resources or credit to implement correctly.
- Requires extension support to ensure that fertiliser requirements are being met.
