Finally, Panel (c) shows a significant deficit of K in the soil and thus the recommendations call for an increase of K fertilizer KCl. In Appendix OA A.2 we discuss the stability over time of the soil analyses.

Column 1 of Table 3 presents the average amount of the three main fertilizers (urea, DAP and KCl) and the total cost of application for farmers in the control group before the intervention in 2014. Column 2 reports the joint balance test that the 2014 amounts applied and costs by farmers in _T_ 1– _T_ 4 are not different than those in the control group. Column 3 reports the average amounts and cost that farmers in _T_ 1 should apply in 2015 according to their plot-level individual recommendations. Column 4 in turn checks that the amounts and costs of applying the plot-level recommendations for farmers in _T_ 1 are not different for those in the control group had the latter received the plot-level recommendations (note that the research team had the soil analysis and the recommendations for controls). Columns 5 and 6 are analogous to columns 3 and 4 for the average-level recommendations instead of plot-level ones. These results suggest that farmers in all five groups were quite similar in terms of fertilizer use in 2014 and in terms of recommended fertilizer packages (based on the soil analyses).

It is clear also clear from Table 3 that the mix of fertilizers traditionally used by farmers is quite different from the recommended mix when using either the plot-level or the clusterlevel recommendations. In particular, farmers in 2014 used 77% (respectively, 92%) more urea than required by the plot-level (cluster-level) recommendations. The corresponding overuse of DAP is equally striking – 61% (164% for the averaged recommendations). In contrast to urea and DAP, farmers used only 28% (31%) of the recommended dose of KCl.<sup>23</sup> These differences between status quo fertilization and individually tailored recommendations are statistically significant as reported in column 8 of Table 3.

The total cost of fertilizer application for the individual recommendations is similar to the investment made by farmers in 2014 (p-value 0.55). This is unsurprising because, as mentioned earlier, the target yield of 4.5 mt/ha was chosen to equate the cost of the recommended fertilizer package with average farmers fertilizer costs. Plot-level recommendations use more fertilizer and are therefore more expensive than the cluster averaged recommendations.<sup>24</sup> That individual recommendations are more expensive than average recommendations is not surprising because recommendations using soil analyses from multiple plots will have, on average, lower nutrient deficits and will thus require lower amounts of fertilizer (see Footnote 10).

Panel B of Table 2 reports that farmers in 2014 waited 36.3 days on average between sowing

> 23On average farmers used 267 Kg/ha of Urea and the individualized (averaged) recommendations were 151.2 kg/ha (138.9 kg/ha). Farmers used 49.4 kg/ha of DAP while the individualized (averaged) recommendations were 30.6 kg/ha (18.7 kg/ha). The corresponding figures for KCl are 9.45 kg/ha and 33.3 kg/ha (individualized) and 30.3 kg/ha (averaged). Both urea and DAP are subsidized by the Mexican government which may explain why farmers use them in such large quantities.

> 24Column 7 reports the p-value of the t-test that individual recommendations in column 3 are equal to the average recommendations in column 5. All p-values are statistically significant at conventional levels.

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