Barren landscape. Credit Anna Ridout, Oxfam

Barren landscape. Credit Anna Ridout, Oxfam

Land degradation is particularly acute in parts of sub-Saharan Africa, where long-term overuse of soil and low, unpredictable rainfall are prime reasons for poor food production. Land degradation affects nearly half of the earth’s land area and reduces the productive capacity of agricultural land by eroding topsoil and depleting nutrients, resulting in enormous environmental, social and economic costs. In sub-Saharan Africa an estimated 180 million people are affected, whilst the economic loss due to land degradation is estimated at US$68 billion per year.[1]

Unless nutrients are replaced, soils become depleted, causing the yields and crop quality to decline.[2] However, farmers are often unable to invest in soil nutrients because they are increasingly costly and often inaccessible. Knowledge amongst smallholder farmers about what inputs to use and how to apply them effectively is limited. Other farmers are unwilling to invest in inputs because they may not be guaranteed a return on their investment.[3] For these reasons, sub-Saharan Africa uses a very small amount of fertiliser, perpetuating the significant soil nutrient deficiencies.

Microdosing in Burkina Faso. Credit The Hunger Project UK

Microdosing in Burkina Faso. Credit The Hunger Project UK

Sub-Saharan Africa uses on average 7kg per hectare of fertiliser, accounting for 3% of the global consumption. In contrast, Asia uses an average of 150kg per hectare.[4]  In June 2006, the African Union adopted the Abuja Declaration committing to increase fertiliser use to 50kg of nutrients per hectare by 2015.[5] Although 50kg per hectare may be excessive in some situations, no region of the world has been able to increase agricultural growth rates and reduce hunger without increasing fertiliser use. African farmers need to use more inorganic fertiliser, but they need to do it sustainably. Farmers must complement existing methods – manure applications and intercropping with nitrogen-fixing legumes or crop residues – with increased but targeted use of fertilisers to return nutrients to the soil,[6] also known as microdosing.

Microdosing of inputs such as fertiliser, pesticide, or water is a highly efficient technique that minimises the application of and over-reliance on inputs. Fertiliser microdosing involves the application of small, quantities of fertiliser onto or close to the seed.[7] This can be done by filling a soda bottle cap with fertiliser and applying it directly to the root of the crop. The same principle can be applied to herbicides that, far too often, are sprayed indiscriminately, killing not only weeds but sometimes damaging the crops themselves.[8] Drip irrigation is a method of water microdosing, applying a limited about of water directly to where it is most needed, reducing wastage and evaporation.

Contribution to Sustainable Intensification

Microdosing helps to raise yields and reduce the environmental impact of excessive input use by increasing the efficiency use of fertiliser, herbicide and water. Fertiliser microdosing uses about one-tenth of the amount typically used on wheat, and one-twentieth of the amount used on maize in the US.[9] Water and fertiliser microdosing can help to improve the soil quality and fertility of highly eroded soils in Africa in a sustainable and affordable way by reducing costs spent on inputs and maximizing the efficiency of their use. To improve the efficiency of the approach and better contribute to Sustainable Intensification, microdosing could be combined with use of organic manure or compost,[10] improved seed and water conservation techniques in arid regions to further increase yields and build natural capital.

Benefits and limitations

The benefits and limitations of fertiliser microdosing have been reviewed and evaluated with hundreds of farmers in West Africa over several years.[11] Microdosing may result in rapid earlier growth compared to crops grown with no inputs, avoiding droughts that may occur early in the season, and increasing crop yields.[12] Yield increases for millet, sorghum and groundnuts[13] are reported across Africa and span a broad range of climatic and soil conditions,[14] suggesting that microdosing is applicable in a variety of conditions.

Reduced inputs

In conventional agriculture systems, excess nutrients in the soil may be leached out during periods of rain and washed into groundwater and surface water bodies. This subsequently depletes the water’s oxygen levels leading to the death of many aquatic organisms and negatively impacting local fisheries and the livelihoods of those that depend on them. Microdosing reduces the overall amount of inputs used, improves nutrient uptake by plants and lowers excess that can cause harm through leaching or run-off. It can also reduce the emissions of nitrous oxide from nitrogen fertilisers and hence help to reduce global warming.


Microdosing is often viewed as an affordable option for poor smallholder farmers[15] as the small quantities of fertiliser required reduces the investment cost. Although the amount required for microdosing may be less than that applied when broadcasting, many farmers in sub-Saharan Africa often lack the finances to buy inputs at all, especially when they are only available in larger, more expensive packages. Farmers are more likely to be able to afford and try fertiliser if it is supplied in small quantities of 5-10kg or less.[16]

Information technology can be used to help make efficient use of the inputs available to farmers. Uganda’s National Agricultural Research Organization (NARO) and the University of Nebraska-Lincoln in the United States have developed a ‘fertiliser optimisation tool.’ This simple computer programme with information about local soil conditions allows farmers to enter the amount of money they can invest, field size, local cost of fertiliser and the market price of their crop. The programme calculates how much fertiliser they should use to get the best return on their investment. Originally developed for farmers in Uganda, the market has expanded and the tool is now being tested in Kenya, Rwanda, Malawi, Zambia, Ghana, Mali, Burkina Faso, Ethiopia, Mozambique, Tanzania, Niger, and Nigeria. There also are efforts underway to develop a version of the tool that can be accessible via mobile phones.[17]


For microdosing to become widely adopted, inputs need to be accessible. Stronger partnerships must also be built between scientists, extension agencies, seed producers and agrodealers to inform and support smallholders. In Mali and Burkina Faso, a collaboration between Alliance for a Green Revolution in Africa (AGRA), INERA (the national agricultural research institute in Burkina Faso),  International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), The Hunger Project and Reseau MARP, used a variety of extension methods such as demonstration plots and farmer schools to train 45,000 farmers in Burkina Faso and more than 25,000 farmers in Mali. Thousands more farmers benefited or were reached through radio broadcasts in local languages. [18] Hub agrodealers that distribute seed and provide training and advice on agricultural best practices are another way of reducing the distance farmers’ travel to access seed and extension services. For example, the Rural Agricultural Market Development Trust (RUMARK), a grantee of AGRA, trains agrodealers in the proper storage and usage of seeds, fertiliser and chemical pesticides. These agrodealers also act as a private extension agent providing valuable knowledge to farmers on how to make the most out of the inputs they sell.[19]

Skill and labour

Microdosing requires relatively little equipment or technical skill compared to conservation agriculture or integrated pest management, and is often seen as a ‘gateway’ method to encourage farmers to use more sustainable farming practices.[20] In contrast, microdosing has also been criticised as being time consuming and laborious.[21] Although only small quantities are required, the inputs must still be applied at the correct volume in the correct location.

Designing and promoting low cost tools that can reduce labour time and costs are therefore needed.[22] The International Crops Research Institute for the Semi-Arid-Tropics (ICRISAT) is exploring the use of incorporating nutrients into the seed coating to reduce labour costs as well as further reducing the quantity of fertiliser to be used.[23] Another time-saving tool is the “top-dressing stick,” designed by One Acre Fund, to help their farmers use the inputs they buy more efficiently. The top-dressing stick is simply a pointed spear with a nail fixed in a perpendicular fashion just before the spearhead. The spearhead creates a hole in the ground where the fertiliser can be placed and the nail helps to measure the distance the fertiliser should be placed from the crop.[24]

Farmers also report that it is sometimes difficult to ensure each plant gets the right dose of input. For example, if too much phosphate (P) is applied, it can lead to poor germination due to seed burning or excessive water absorption by the seed coating.[25] In sub-Saharan Africa, the opposite is more likely to occur as smallholder farmers are inclined to use as little fertiliser as possible in order to save money. According to a survey on inorganic fertiliser application in Fakara, Niger, the amount of fertiliser applied by farmers through microdosing is less than the recommended level essential to obtain optimal improvement of millet production: 9kg Phosphate (P2O5) per hectare.[26] Over the long term, ‘under-application’ could lead to nutrient depletion in the soil.[27] ICRISAT is also experiment with packaging the required dose of fertiliser as a tablet to omit the need for correct measurement.

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Case Studies

Download These Case Studies (pdf)
Case Study 1: Herbicide microdosing to control Striga

Striga, a parasitic weed. Credit IITA

Striga, a parasitic weed. Credit IITA

Striga is a weed that infests up to 40 million hectares of farmland in sub-Saharan Africa. It leads to yield losses between 20% and 100% and affects 100 million livelihoods, causing US$1 billion in annual crop losses. Some of the solutions developed so far include the use of Imazypyr (a non-selective herbicide used for the control of a broad range of weeds), but this can kill or damage the crop.[1]

The roots of several legumes, such as Silverleaf desmodium, are effective in suppressing Striga and have been incorporated into push-pull, intercropping system. The desmodium neutralizes the Striga and Napier grass serves as a lure for pests such as the maize stalk borer. Whilst promising, desmodium can be difficult to establish as small, slow growing desmodium seedlings vulnerable to invasive weeds.

Recently a mutant gene in maize that provides Imazypyr resistance (IR) was developed by tissue culture and bred into local maize varieties such as IR breed KSTP 94 developed by the Kenya Agricultural Research Institute (KARI). The International Wheat and Maize Center (CIMMYT) developed a novel approach of coating these newly resistant maize seeds with the Imazypyr herbicide before distribution. When the non-resistant Striga seeds germinate, they attach to the maize roots and take up the herbicide from the seed coating. The Striga is killed and the maize grows with little or no impact from the herbicide.

On-farm use of IR maize enables Striga-affected farmers in Kenya to increase harvests from an average of 500kg per hectare to 1,500kg per hectare. If 20% of severely infested land in western Kenya is cultivated with IR maize, it is possible to produce an extra 60,000 tonnes of maize or enough to feed at least 100,000 households. Grace Lugongo, a farmer from Butula in western Kenya explains, “Until 2007, I had never known the meaning of harvesting a full sack of maize from my 0.5ha piece of land thanks to the ‘Striga’ weed. All my efforts would yield only 2 ‘gorogoros’ (a tin measuring about 2kg) of maize. I decided to try the IR maize and over the years my yields have increased to 10 bags from the same piece of land. From the harvest I am able to cater for my subsistence needs and also afford some surplus to sell to cater for my other needs such as school fees for my children.”

Dick Morgan, from Vihiga, a town in western Kenya explained, “Before a new maize variety was introduced to me I used to plant maize without success. This was very frustrating as maize is our main food. In 2005 my fortunes in maize farming started to change after I was introduced to the IR maize which I tried and saw a significant increase in maize yields and also in the reduction of the Striga weed on my farm.”[2]

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Case Study 2: Impact of fertiliser microdosing on crop yields in the Sahel
Woman farmer takes home pearl millet. Credit ICRISAT

Woman farmer takes home pearl millet. Credit ICRISAT

Less can be more if the appropriate fertiliser is applied at the right time, in the right quantity and in the right place. In sub-Saharan African, fertiliser microdosing developed by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and partners has increased agricultural productivity. In order to improve the productivity of pearl millet and sorghum, at least 100kg of NPK is required per hectare, but Dr Ramadjita Tabo, ICRISAT’s Director for West and Central Africa, recognized that the cost of $40 per hectare to meet this requirement was prohibitive to smallholders. Further, the region’s sandy soils were phosphorous deficient so ICRISAT recommended that farmers use 6g of NPK (15-15-15) plus 2g of DAP and 1g of Urea, just a 3-finger pinch, resulting in only 2g required per plant and limiting total fertiliser use to just 20g per hectare.

On-farm tests were carried out to assess the effect of microdosing in the semi-arid climate of Mali, Burkina Faso and Niger.[1] In the Sahel, soils are sandy with poor fertility and low levels of rainfall (500mm-800mm annually).[2] In these trials, farmers selected the plant variety and fertiliser type according to what was available in their country. The table below displays the rates of fertiliser application per country. Fertiliser microdosing on average was found to increase yield for millet, sorghum, maize, cowpea and groundnut between 44% and 120%.[3]

Country Fertiliser microdose
Burkina Faso 4 g of nitrogen, phosphorus, and potassium fertiliser (NPK) (15-25-15)
Mali 4g of NPK (17-17-17)
Niger 6g of NPK (15-15-15), 2g Di Ammonium Phosphate (DAP) (18-46-0), and 2g DAP + 1 g Urea (46-0-0)
Note: (15-25-15) signals the blend of Nitrogen, Phosphorus, and Potassium. For example, if you purchased a 50-pound bag, 15 pounds (or 15%) would be Nitrogen, 25 pounds would be phosphorus, and 15 pounds would be potassium. The remaining 45% is simply filler, which are there mostly to help disperse the chemicals.
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Case Study 3: Conservation Agriculture and Microdosing in Zimbabwe
Microdosing & Conservation Agriculture in Zimbabwe. Credit ICRISAT

Microdosing & Conservation Agriculture in Zimbabwe. Credit ICRISAT

In Zimbabwe, an estimated 75%-90% of crops remain unfertilised each season and when used, farmers on average only apply 3kg of nitrogen fertiliser per hectare, compared to average rates of 9kg per hectare for all of sub-Saharan Africa. The usage rates are low and variable due to limited knowledge of appropriate use, lack of availability and affordability as well as cultural and traditional beliefs that fertilisers ‘burn’ the crops.

Since 2004, the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has been working in partnership with the UK Department for International Development (DFID), the national extension service and NGO’s to promote conservation agriculture amongst smallholder farmers. Conservation agriculture consists of 3 principles: minimum soil disturbance, legume-based intercropping and application of organic mulch to improve soil fertility. In 2011, more than 150,000 smallholders practiced conservation agriculture, raising cereal yields 15% to 100% across different regions. When combined with microdosing – the precise application of small amounts of fertiliser that smallholders are likely to be able to afford – farmers in Zimbabwe significantly improved household food security.

To increase the adoption of fertiliser use, ICRISAT provided training on microdosing for more than 650 lead farmers, 241 government extension officers and 119 extension officers from 16 local and international NGOs. From 2003-2007, more than 160,000 households received 25kg bags of nitrogen fertiliser and flyers in local languages explaining how to apply the fertiliser.   Despite poorer than average rainfall during the 2006/2007 cropping season, farmers experienced yield increases between 30% and 50%. During the same season, more than 170,000 households increased cereal production by an estimated 40,000 tonnes, saving US$7 million in annual food imports and significantly improving food security. As of February 2013, close to 300,000 farmers are now using both technologies and have achieved productivity gains of up to 100%. Nevertheless, challenges to adoption still remain; the programme is therefore trialling smaller packs of fertiliser between 5g-20g as well as trying to reduce the labour constraints to adopting all 3 tenets of conservation agriculture. [1]

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