conducted by Bold et al. in 2014 in Uganda in which 100% of the 369 samples tested were found to be missing nitrogen, and missing on average 30% of their nitrogen, an outlier result in published studies and reports.<sup>17</sup>

# **Multi-nutrient fertilizers**

Evidence regarding the measured agronomic quality of multi-nutrient fertilizers suggests the presence of far more quality issues than in urea. Michelson et al. (2021) report results of tests of DAP and CAN collected in Tanzania and find 15% of DAP samples out of compliance and 63% of CAN samples. While frequency is relatively high, severity is relatively low: mean nitrogen deviations are 7% for DAP and 6% for CAN. Asante et al. (2021) find that NPK sampled in Ghana (15 samples) meets standards for nitrogen, phosphorous, and potassium. Apart from Michelson et al. (2021) and Asante et al. (2021), nearly all published evidence regarding the quality of multi-nutrient fertilizers comes from IFDC reports on West Africa (2013), Uganda (2018), and Kenya (2018). IFDC reports that quality problems are most frequent in NPK fertilizers manufactured through blending; 51% of the 106 samples of NPK 15:15:15 (the most commonly found NPK fertilizer in West Africa in the study) were out of compliance based on the ECOWAS standards as were 86% of the 20:10:10 blend samples and 96% of the 15:10:10 blend samples. More work is required to understand the degree to which these widespread but generally modest shortages are economically and agronomically significant.

The IFDC report on the quality of fertilizer in West Africa (Sanabria et al. 2013) argues that nutrient deficiencies in some blends is likely attributable to uneven distribution of granules in the bags due to improper blending (mixing). In such cases, the nutrient composition of the entire bag may be in compliance with the labeled nutrient content but non-uniform distribution within the bags means that samples taken from the bag are not in compliance. In addition, small farmers purchasing blends from open bags or in repackaged smaller bags are likely to receive products with nutrient contents that do not reflect the manufactured standard. Nutrient deficiencies in blends can also be attributable to manufacturing problems, poor control of blending procedures, and poor-quality blending equipment. Quality issues were much less prevalent in the compound fertilizers sampled in the IFDC studies.<sup>18</sup> Results from IFDC studies in Uganda and Kenya are consistent with the findings of quality issues arising in blends, likely due to problems in manufacturing (Sanabria et al. 2018a and 2018b).

> 17 Sanabria et al. (2018) write in their Uganda fertilizer assessment of the Bold et al. (2017) findings of these widespread and significant nitrogen shortages in urea: “the report does not identify or quantify the presence of materials that may be used to dilute nitrogen content in the urea samples. Dilution is the only possible way of reducing nitrogen content in urea. The nitrogen content in the samples used as evidence could be below 46% as a result of deficiencies in the use of the Kjeldahl method, especially when the method is applied manually and by personnel with limited experience analyzing fertilizers. A very common mistake is assuming that a lab with experience analyzing soils will perform well analyzing fertilizers.” In fact double testing of NPK samples by Asante et al. (2021) showed discordance between results of samples double tested in a Canadian lab and a Ghanaian lab. Both labs had used the Kjeldahl method. The Ghanaian lab initially identified significant nitrogen deficiencies but retested the samples after the Canadian lab found that the samples met nitrogen standards. Upon retesting, the Ghanaian lab identified a problem with the nitrogen digester and found that nitrogen levels were also good in the samples.

18 Crystal and liquid fertilizers, which comprise a small share of the market, were found to have significant quality issues with considerable nitrogen shortages documented in Kenya (Sanabria et al., 2018a).

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