Loy digging was in fact a form of Ploughing - done with a spade around 150+ years ago . Practised in Famine times . Done with a special spade as can be seen . The potato seed was placed on the ground and when the trench was dug - the sod was turned back on it - so it was between two layers of grassy sod - plenty of Organic matter etc . Yields were in fact quite good for that time - around 6 tons / acre .