Search

Soilborne potato diseases and soil microbial community characteristics were evaluated over 8 years in different potato cropping systems designed to address specific management goals of soil conservation, soil improvement and disease suppression. Results were compared to a standard rotation and non‐rotation control in field trials in Maine. Standard rotation consisted of barley underseeded with red clover, followed by potato (2‐year). Soil‐conserving system (SC) featured an additional year of forage grass and reduced tillage (3‐year, barley/timothy–timothy–potato). Soil‐improving system (SI) added yearly compost amendments to SC, and the disease‐suppressive system (DS) featured crops with known disease‐suppressive capability (3‐year, mustard/rapeseed–sudangrass/rye–potato). Systems were established in 2004, evaluated with and without irrigation, and actively managed until 2010, with potato also planted in 2011 and 2012 to examine residual effects. All rotations reduced soilborne diseases black scurf and common scab, and increased yield after one rotation cycle (3 years), but diseases increased overall after two rotation cycles. DS maintained lower soilborne disease levels than all other rotations, as well as high yields, throughout the study. Cropping system effects became more pronounced after multiple cycles. SI system and irrigation both resulted in higher yields, but also higher levels of soilborne disease. Cropping system and irrigation effects were significant even after systems were no longer maintained. Soil microbial community data showed significant changes associated with cropping system, and differences increased over time. Cropping system strategy had significant and lasting effects on soil microbiology and soilborne diseases, and can be used to effectively enhance potato production.

This work evaluated the level and nature of water-extractable soil organic matter (WEOM) from a 6-yr potato ( L.) crop rotation field experiment. The content of WEOM was higher in continuous potato soils than in the 2-yr and 3-yr crop rotation soils except for those crop rotation soils with soil improvement management by composted manure. Irrigation increased the level of WEOM in crop rotation soils. Ultraviolet–visible and fluorescence parameters indicated that WEOM in continuous potato soil possessed a high degree of humification and that crop rotation increased the aromatic and low molecular mass portions. In most irrigated soils, WEOM contained less aromatic but higher humified components. Characterization of the WEOM samples with crop rotation and irrigation suggests that these management practices stimulate the decomposition of the humic fraction in soil organic matter pools, implying healthier soil conditions with these management practices than with continuous potato growth.

Soil borne diseases can greatly reduce marketable yields and are a major concern to Maine potato (Solanum tuberosum L.) producers. Control of these organisms is difficult as they can persist in the soil for several years and symptoms typically worsen each year. Depending on the specific pathogen, different mechanisms for moderating soil borne disease can be employed, such as breaking the hostpathogen cycle, stimulating beneficial microbial activity, and direct inhibition of the pathogens. Current research at the USDA-ARS New England Plant, Soil, and Water Laboratory is investigating the effect of rotation crops and rotation sequences on the incidence and severity of soil-borne diseases in the following potato crop. These results (incidence, severity, and potato yield) are incorporated into an economic simulation model to determine the impact of rotations on profitability, level of income risk, and probability of economic loss for different rotation sequences and rotation lengths. The results show that several rotation sequences can increase profitability and reduce economic risk when compared to continuous potato or to the standard barley-potato rotations.