As noted above, powdering and granule segregation can lead to uneven distribution of nutrients in fertilizer bags. This can be important both for sampling to assess quality and for small farmers who may purchase fertilizer in small quantities of one or two kilograms scooped directly from open bags or repackaged for sale, or for famers who purchase larger quantities but with use spanning a longer time period, such as multiple agricultural seasons. IFDC notes a relationship between high moisture content of the samples and high caking. Moisture content and granular segregation were found to have a negative relationship with nutrient content in NPK blends in West African samples (Sanabria et al. 2013) but this mapping is not clear. Urea, for example, often exhibits caking and granular degradation without any deviations in nitrogen content. Samples with observed quality issues related to powdered granules and discoloration are often found to have good nutrient content and samples with no observable problems (especially blends) can be found to have deficiencies. Evidence in Michelson et al. (2020) suggests that farmers use these observables as a signal of unobservable nutrient content (more below on farmer assessment).

# **V. Pesticide Quality Measurement and Evidence**

Glyphosate herbicide is generally sold in concentrations of 36 and 43.9 percent glyphosate by weight. Glyphosate formulation verification is done in a lab using high-pressure liquid chromatography with ultraviolet detection. The method compares tested samples to a reference sample and is the standard procedure to measure glyphosate concentration (Morlier and Tomkins, 1997). Samples are tested in duplicate. Haggblade et al. (2018) use this method to test 100 samples of glyphosate acquired in Mali and Ashour et al. (2019b) use the method for their 483 Ugandan samples. Haggblade et al. (2018) note that Mali had no accredited lab to test for glyphosate concentration and so samples were tested both in a West African lab outside of Mali and also in the United States. Costs for glyphosate testing are high relative to fertilizer testing: $175 per test at a private Ugandan lab (2014), $195 per test in a private U.S. lab, and $50 per test at a Ugandan university laboratory.

Several recent studies and reports ( _Counterfeit Pesticides Across Europe_ 2008; Fishel 2008) argue that counterfeit pesticides are increasing globally. Only a handful of academic studies have tested the quality of pesticides for sale in markets in low-income countries. These studies have primarily focused on glyphosate. Haggblade et al. (2018) test 100 samples of glyphosate collected from four primary agricultural markets in Mali and find that one-third contained either too much or too little of the active ingredient. They find a large experimental error in the tests conducted however, and stress that improvements in laboratory testing capability in West Africa are critical. Ashour et al. (2019b) find that sampled bottles (483 samples from 120 markets in 25 districts in Uganda) are missing on average 15% of the advertised amount of glyphosate, with 31% of the samples containing less than 75% of the advertised concentration. Ashour et al. are unable to distinguish between counterfeiting, adulteration, storage problems, or manufacturing errors.<sup>22</sup>

> 22 Ashour et al. also found that some glyphosate samples had a concentration of the active ingredient that exceeded the manufacturing standard. One way this can happen for pesticides is improper storage and product expiration, which can lead to evaporation of some water from the product, leaving a higher concentration of the active ingredient. There could be other reasons, but this was one that was offered.

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