Posted: 10/05/2017 at 19:05
The reason that traditionally grown potatoes are said to 'clean the ground' is because the soil has to be cultivated and kept loose so that the potatoes can be earthed up, therefore the gaps between the roes are regularly hoed to be kept free of weeds and the soil is moved about to earth up the potatoes throughout the growing season.
Also as the potatoes grow the foliage becomes thick and one row of potatoes meets the next one, shading out any germinating weeds around them.
Then when the potatoes are lifted the beds are dug over again to get all the tubers, preventing any 'volunteers' growing ... again this keeps the soil cultivated preventing weed growth.
Afraid it's not some magical property that the potatoes have .......... it's the hard work of the gardener that cleans the soil.