Cropping History Affects Potato Yields in Canterbury, New Zealand

High-yielding potato crops in Canterbury have achieved 90 t ha −1 or more. However, soil-borne diseases and poor soil structure are primary factors responsible for reducing this potential to an average of 55 t ha −1 . The interaction between these factors was measured by growing the cultivars ‘Russet Burbank’ and ‘Innovator’ in 15 fields, grouped into four categories related to cropping history that influences soil health: soil-restorative (>7 years of grass) and non-restorative (>6 annual crops) with presence or absence of potato crops in the previous 10 years. Although predominantly grass histories with previous potato crops showed greater severity of soil-borne diseases than annual crop history without previous potatoes, this did not lead to yield losses. Improved soil quality increased yields by an average 10 t ha −1 regardless of disease pressure. Modelling suggested that early planting, maintaining crop canopies and managing water supply were also key factors for achieving high potato yields.