Grow Organically

The answer lies in the soil

Rules for Crop Rotation

Never follow this years crop with another member of the same family.
Arrange your plan so that heavy feeders always follow legumes, which enrich the soil.
Potatoes yield best after sweetcorn.
Grain crops do best after legumes.
Root crops often take a lot out of the soil, so put them before legumes.
Having brassicas follow onions is beneficial.
Tomatoes are narcissistic and do not like to rotate.
Cucumbers and squashes are beneficial to most following crops.