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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