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Fig. 6. The under- or overestimation of pH and lime requirement (LR) following map development based on area composite (AC), point (P) or centers point (CP) sampling strategies for DPAC. Composite strategies include a research whole field (AC WF, all samples averaged), a commercial or true farm whole field (AC TF, subsets of samples representing a density of 1 ha–1 averaged), and 1-ha grid (AC 1 ha, all samples averaged on a ha–1 basis). Maps developed from point data use either the CP value of a given ha to represent the whole ha without any smoothing (No. Smth CP1ha), IDP = 2 applied to CP 1-ha data, or kriging applied to P 0.2 and 0.4 ha data. Box plots show error mean (...), median (—), 25th to 75th percentiles (
), 10th and 90th percentiles (
,
), and 5th and 95th percentiles (•). A cross (
) next to the AC TF mean absolute error (MAE) indicates µAC TF 
0 (p < 0.05). Underlined MAEs of other strategies indicates µother µAC TF (p < 0.05). All prediction efficiencies (PE) are calculated relative to AC TF, and underlined PEs indicate 
other TF (p < 0.05).
