Key points
- Year two of this three year SFF project focused on soil structure and rotation history for 15 sites in Canterbury. There were four-plot trials at each site (Russet Burbank and Innovator, treated with formalin and untreated).
- The major influence on yield was soil quality, and seedsoil borne disease had little impact.
- The crop history score x soil structural condition score factor explained 39% of the yield variation for Innovator and 52% for Russet Burbank. If soil quality is poor then growers should consider growing Innovator in preference to Russet Burbank.
- There was a good correlation between yield and a 10 year crop history score, and between yield and a oneoff soil structural condition score, showing that these two independent methods could be useful for gauging paddock suitability for growing potatoes.
- More grass in a ten year history improved soil resilience and enhanced rooting hospitality for potatoes, thus enabling the crop to access more resources. For Russet Burbank, this equated to an average 3.5 t/ha lift in yield for every year in the previous ten year history a field was in grass.
- Formalin dipping did not significantly control these diseases in the glasshouse or the field.
- Seed could have transferred Rhizoctonia solani, causing stem canker, and Spongospora subterranea, causing root galls, to the field, as all glasshouse plants were infected with these diseases.
- Stem canker and root gall incidence and severity was greater from an ex-potato paddock history compared with no potato history, but yield was unaffected.
- Disease severity was higher in fields with predominantly grass histories, compared with mainly cropping histories. However, gross yield was greater from ex-grass (86 t/ha) than from ex-crop fields (75 t/ha).