Kenya (using SoilDoc, a low-cost soil testing tool) has a positive effect on the willingness to pay for inputs (DAP and manure, among others) but they do not measure longer-term fertilizer use or productivity. Our work is perhaps closest to Harou et al. (2018) who offer soil analyses, fertilizer recommendations (using SoilDoc) and an in-kind grant that covers the cost of fertilizer for approximately 0.2 ha.<sup>14</sup> We complement their work by measuring the impact of recommendation specificity, assessing the effect of autonomy and examining both shorter-run outcomes as well as longer-term persistence.

We also contribute to the literature on mis-allocation (see e.g. Restuccia and Rogerson, 2017, for a survey) by providing micro-evidence on the inefficient use of fertilizer in agricultural production. In our context, since farmers were already familiar with inorganic fertilizer, our intervention recommended changes in the intensive margin (i.e. input mix), rather than the extensive margin, at no extra cost because the value of the recommendations was similar to the average amount that farmers spent on fertilizer. We believe that documenting such misallocation of fertilizer is important both from the perspective of the individual farmer who could improve productivity by reallocating inputs, as well as that of the social planner since the over-use of urea and the consequent nitrogen leaching and surface run-off could have significant negative environmental consequences (see e.g. Wang and Li, 2019, for a review of the evidence).

Our results also contribute to the debate about the appropriate level of specificity when testing soil quality and providing input recommendations. Harou et al. (2018); Duflo et al. (2011); Marenya and Barrett (2009); Sheahan et al. (2013) all find that official recommendations are too generic (typically at a state or country level) to account for local soil heterogeneity. Smallholder farmers in the developing world typically fertilize using average recommendations, with no information on which elements are most needed, and primarily use urea and DAP. Ours appears to be the first paper to compare plot to cluster level recommendations using field experimental evidence.

Finally, we contribute to the literature on autonomy, which has emphasized both its intrinsic as well as its instrumental value on participatory decision-making (broadly construed), compliance (Malesky and Taussig, 2019; Dal Bó et al., 2010), effort (Sjöström et al., 2018) and productivity (e.g. Black and Lynch, 2001; Bonin et al., 1993; Spector, 1986). Using observational data from an agricultural context, Bardhan (2000) finds that Indian farmers are less likely to violate irrigation rules when they themselves have crafted those rules. The reactance literature in psychology (Wicklund, 1974; Fitzsimons and Lehmann, 2004) argues that recommendations by experts may backfire as agents purposefully try to contradict them. We show that providing autonomy in the decision to follow expert advice may in fact lead to higher adherence in the

> 14They study Tanzania, where fertilizer usage is low (less than 1 percent of study farmers had used fertilizer at baseline) and thus the recommendations suggest substantial increases in input use.

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