Impacts of Primary Non-Inversion Shallow Tillage and Moldboard Plowing on the Potato Early Dying Disease Complex in Prince Edward Island, Canada

Conservation tillage has shown potential to improve soil health and enhance crop productivity in various cropping systems. Moldboard plowing (MP) in the fall prior to the potato phase is a conventional practice in Prince Edward Island (PEI), Canada, which leaves the soil prone to erosion and soil organic matter decline. Potato early dying disease complex (PED) is a major yield limiting factor in potato production in PEI. The objective of this four-year (2019–2022) study conducted in 14 commercial fields was to determine the effect of non-inversion shallow tillage (ST) in comparison with MP on PED pathogen population density in the spring at potato planting time and in the fall post-potato harvesting, and on PED disease severity. Root lesion nematodes (Pratylenchus spp., RLN) were detected in all fields. Verticillium dahliae was the predominant species in all fields, while V. albo-atrum was sporadically detected in a few samples. The population density of the RLN and V. dahliae varied among the fields. In the spring samples, V. dahliae density was significantly higher in 5 of the 14 fields with the ST treatment compared with MP. RLN density was significantly higher in one of the 14 fields with the ST. When averaged across all fields, V. dahliae density was 1.8-fold higher with ST than with MP (p = 0.018), but no differences were detected for RLN density between ST and MP. In the fall after the potato harvest, only two fields had significantly higher V. dahliae density with the ST than with MP, and no differences were detected for RLN density between ST and MP. When combined data across all fields were analyzed, no differences in pathogen population levels were detected between ST and MP for both V. dahliae and RLN. Higher PED severity was detected in three fields associated with ST. However, when disease ratings were averaged across all fields, no PED severity difference was detected between ST and MP. The PED severity was significantly positively related to the spring population density of V. dahliae and RLN, but not with the tillage regimes in this study. Further study is needed to determine the long-term effect of tillage regimes on soil health, disease development, soil disease suppressiveness, pathogen population dynamics and PED development in potato production.