A comparison of soil maps, kriging and a combined method for spatially predicting bulk density and field capacity of ferralsols in the Havana–Matanzas Plain

Predictions of soil bulk density and field capacity at 0–10, 10–20 and 20–30 cm depths in Rhodic and Xhantic Ferralsols at the Havana–Matanzas plain are validated at a number of measured sites. It was done in order to compare the prediction accuracy under the constraint of a small data set by the following three procedures: (1) soil maps, (2) kriging, considering Xhantic and Rhodic Ferralsols as different soil types, as well as Ferralsols as a combined single soil type and (3) combined kriging–soil map predictions. The results show a considerable bias in the predictions made with the soil map, which is not found in kriging predictions. Generally, soil map predictions are also less accurate. However, the use of soil maps in Xhantic Ferralsols field-capacity predictions was the most reliable approach. The use of semivariograms for each soil type in kriging predictions only yields more accurate results for Rhodic Ferralsols, where enough data is available. The combined kriging–soil map procedure yields the smallest bias. Predictions of the combined procedure are more accurate, although accuracy differences found with the other two approaches were not very large. The combined kriging–soil map approach yields better predictions than the others for this case study.