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.
Unless nutrients are replaced, soils become depleted, causing the yields and crop quality to decline. 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. For these reasons, sub-Saharan Africa uses a very small amount of fertiliser, perpetuating the significant soil nutrient deficiencies.
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. In June 2006, the African Union adopted the Abuja Declaration committing to increase fertiliser use to 50kg of nutrients per hectare by 2015. 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, 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. 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. 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. 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, improved seed and water conservation techniques in arid regions to further increase yields and build natural capital.
The benefits and limitations of fertiliser microdosing have been reviewed and evaluated with hundreds of farmers in West Africa over several years. 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. Yield increases for millet, sorghum and groundnuts are reported across Africa and span a broad range of climatic and soil conditions, suggesting that microdosing is applicable in a variety of conditions.
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 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.
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.
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.  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.
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. In contrast, microdosing has also been criticised as being time consuming and laborious. 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. 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. 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.
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. 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. Over the long term, ‘under-application’ could lead to nutrient depletion in the soil. ICRISAT is also experiment with packaging the required dose of fertiliser as a tablet to omit the need for correct measurement.