The Potato Systems Planner: Cropping System Impacts on Soilborne Diseases and Soil Microorganisms Robert Larkin, Tim Griffin, John Halloran, and Wayne Honeycutt, USDA-ARS New England Plant, Soil,

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The Potato Systems Planner Cropping System
Impacts on Soilborne Diseases and Soil
Microorganisms Robert Larkin, Tim Griffin, John
Halloran, and Wayne Honeycutt, USDA-ARS New
England Plant, Soil, Water Laboratory Orono,
Maine
CONCLUSIONS Crop rotations have substantial and
varying impacts on soil microbial communities and
soilborne potato diseases depending on the
specific crop. Each crop resulted in unique soil
microbial characteristics. Canola and rapeseed
crops prior to potato were most effective in
reducing soilborne diseases, whereas soybean,
green bean, and red clover resulted in high
disease levels (comparable to continuous
potato). In 3-yr rotations, cropping sequence
(order) is also important. The crop immediately
preceding potato has the greatest impact on
potato diseases. Less desirable rotation crops
can be used if not preceding potato. Results of
this research may be useful for making cropping
system management decisions and are available in
the Potato Systems Planner CD.
SUMMARY Different 2-yr and 3-yr crop rotations,
consisting of barley/clover, canola, green bean,
millet, soybean, and sweet corn in various
combinations followed by potato, were evaluated
for their effects on the development of soilborne
potato diseases and soil microbial communities
over several cropping seasons in Maine. All
rotations significantly affected soil
microorganism populations and activity, resulting
in unique microbial profiles. Rotations with
canola or rapeseed preceding potato were most
effective at reducing the soilborne diseases stem
canker and black scurf, caused by Rhizoctonia
solani, and common scab, caused by Streptomyces
scabies (25-75 reduction relative to continuous
potato). Barley, millet, and sweet corn rotations
were somewhat effective in reducing disease
(15-40 reduction). However, potato following
soybean, green bean, or red clover, resulted in
high disease levels of stem canker and black
scurf. These results, along with data on yield,
nitrogen recycling, and economic viability, were
used to develop The Potato Systems Planner, an
interactive CD-Rom decision-support tool to aid
in establishing improved cropping and disease
management systems for potato production. Also
included in the Planner CD is a Potato Disease
Database, containing descriptions, symptoms, and
management information for 19 of the most common
potato diseases. Potato disease information was
compiled and edited from The Compendium of Potato
Diseases (2nd Ed. 2001, APS Press). The Planner
CD is available upon request (email
Wayne.Honeycutt_at_ars.usda.gov). Soil
Microbiological Parameters Measured Populations
of total culturable bacteria and fungi from
dilution plate counts Soil microbial activity,
substrate utilization profiles from GN2 Biolog
plates Soil microbial community characteristics
from fatty acid methyl ester (FAME) profiles.
Potato Cropping Systems Research
2-yr rotations (2 entry pts) est.1997, 1998
Newport, ME RCB, 4 reps. Plots 24.4 x 3.7 m,
Russet Burbank potato
Barley w/red clover (underseeded) - Potato Canola
- Potato Green Bean - Potato Millet (1997-2000),
Rapeseed (2001) Sweet Corn - Potato Soybean -
Potato Potato - Potato
Related Publications Larkin, R.P. 2003.
Characterization of soil microbial communities
under different potato cropping systems by
microbial population dynamics, substrate
utilization, and fatty acid profiles. Soil Biol.
Biochem. 351451-1466. Larkin, R.P., and
Griffin, T.S. 2006. Control of soilborne diseases
of potato using Brassica green manures. Crop
Protection (In Press). Larkin, R.P., Griffin,
T.S., and Honeycutt, C.W. 2006. Crop rotation and
cover crop effects on soilborne diseases of
potato. Phytopathology 96S64 (Abstract).
Larkin, R.P., and Honeycutt, C.W. 2006. Effects
of different 3-yr cropping systems on soil
microbial communities and Rhizoctonia diseases of
potato. Phytopathology 9668-79.
3-yr rotations (2 entry pts) - est.1998 Presque
Isle, ME RCB, 4 reps. Plots 30.5 x 3.7 m, Russet
Burbank potato
Soybean - Canola Soybean - Barley Green bean -
Sweet corn Potato - Potato
Barley - Clover Sweet corn - Canola Canola -
Sweet corn Sweet corn - Soybean
B Microbial activity
a
A Bacteria populations
a
B Common scab
A Black scurf
ab
a
a
ab
b
b
bc
a
b
a
c
b
c
ab
ab
ab
ab
ab
ab
c
a
b
ab
bc
ab
Optical density
d
bc
b
b
c
b
c
b
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bc
c
Propagules/g soil (x106 )
d
Disease incidence ( of tubers)
e
d
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Disease severity ( coverage)
c
c
d
b
cd
c
d
b
Fig. 1. Effect of different 2-yr crop rotations
on the severity of soilborne tuber diseases, A)
black scurf and B) common scab averaged over 6
field seasons (2000-2005).
Fig. 2. Effect of different 2-yr crop rotations
on A) soil bacterial populations and B) soil
microbial activity (as represented by average
substrate utilization in Biolog plates) measured
following the rotation crop and potato crop (3-yr
avg).
Fig. 3. Effect of different 3-yr crop rotations
on the incidence of black scurf averaged over 3
field seasons (2001-2004).