Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 29, 2010
Publication Date: November 5, 2010
Citation: Larkin, R.P., Griffin, T.S., Honeycutt, C.W. 2010. Rotation and cover crop effects on soilborne potato diseases and soil microbial communities. Plant Disease. 94:1491-1502. Interpretive Summary: Soilborne diseases are persistent problems in potato production, and sustainable management options are needed. The use of crop rotations and cover crops to actively alter or manipulate soil microbial communities in an attempt to develop natural disease-suppressive soils is a promising management approach. In this research, seven different 2-yr rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were assessed in long-term cropping systems trials (1997-2006) for their effects on soilborne potato diseases, tuber yield, and soil microbial communities. These same rotations were also assessed with and without the addition of a fall cover crop of no-tilled winter rye over a 4-yr period. Canola and rapeseed rotations consistently reduced multiple soilborne potato diseases (18-38%). Canola rotations also increased tuber yield relative to continuous potato and barley rotations. Addition of a fall cover crop to each rotation further reduced soilborne diseases by 5-19%. Rotation and cover crops also significantly affected soil microbial community characteristics, including bacterial and fungal populations, microbial activity, and soil fatty acid profiles, which indicate microbial community structure. This research demonstrated that different rotation and cover crops significantly affect soilborne diseases and soil microbial communities, and that combining an effective rotation crop, such as canola or rapeseed, with a fall cover crop, can substantially improve control of soilborne diseases. These results have immediate practical applications in potato production, as well as important implications for the future development of sustainable potato cropping systems.
Technical Abstract: Seven different 2-yr rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were assessed in long-term cropping systems trials (1997-2006) for their effects on the development of soilborne potato diseases, tuber yield, and soil microbial communities. These same rotations were also assessed with and without the addition of a fall cover crop of no-tilled winter rye over a 4-yr period. Canola and rapeseed rotations consistently reduced the severity of Rhizoctonia diseases (stem canker and black scurf) and common scab (18 to 38% reduction), and canola rotations resulted in higher tuber yields than continuous potato or barley/clover (6.8 to 8.2% higher). Addition of the winter rye cover crop further reduced black scurf and common scab, averaging 12.5 and 7.2% reduction, respectively, across all rotations. The combined effect of a canola or rapeseed rotation and winter rye cover crop reduced disease severity by 35 to 41% for black scurf and 20 to 33% for common scab relative to continuous potato with no cover crop. Barley/ryegrass and rapeseed rotations resulted in the highest soil bacterial populations and microbial activity, and all rotations had distinct effects on soil microbial community characteristics. Addition of a cover crop also resulted in increases in bacterial populations, microbial activity, and had significant effects on soil microbial characteristics, in addition to slightly improving tuber yield (4% increase). Thus, in addition to positive effects in reducing erosion and improving soil quality, cover crops in conjunction with effective crop rotations, can provide improved control of soilborne diseases.