Digital soil mapping of coarse fragments in southwest Australia: Targeting simple features yields detailed maps

•Soil coarse fragment data tend to be unreliable, and difficult to model and map.•Survey and agronomic observations increased the dataset × 10 (n = 39,880)•Predicted 3D coarse fragment layers outperformed other maps and were plausible.•New predictions achieved overall accuracies 0.74 to 0.92 and AUC 0.79 to 0.89.•Mapping soil features is a useful compliment to continuous property prediction.