Transcript New England Plant, Soil, & Water Laboratory Orono, Maine

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
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 decisionsupport 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: [email protected]).
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 - Clover
Sweet corn - Canola
Canola - Sweet corn
Sweet corn - Soybean
Black scurf
2
ab
bc
ab
c
c
ab
70
Common scab
5
ab
a
ab
ab
ab
4.5
4
b
b
1.5
3.5
1
Barley/clover
Sweet Corn
Millet-rapeseed
5.5
a
2.5
B
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. 35:1451-1466.
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 96:S64 (Abstract).
3
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).
60
50
40
a
A
b
Canola
Soybean
Green Bean
Millet-rapeseed
Potato
0.5
B Microbial activity
Bacteria populations
b
c c
a
d
b
b b b
d
c
c
0.45
0.4
0.35
b
a
ab
bc
a
c
d
30
0.25
20
0.2
b
bc
e
0.3
ab
bc
c
d
Rotation
Potato
Rotation
Potato
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).
Disease incidence (% of tubers)
6
Results of this research may be useful for making cropping system
management decisions and are available in the Potato Systems Planner CD.
Soybean - Canola
Soybean - Barley
Green bean - Sweet corn
Potato - Potato
Optical density
A
Green Bean
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.
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 96:68-79.
Propagules/g soil (x106 )
Disease severity (% coverage)
3
Canola
Soybean
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).
Barley w/red clover (underseeded) - Potato
Canola - Potato
Green Bean - Potato
Millet (1997-2000), Rapeseed (2001+)
Sweet Corn - Potato
Soybean - Potato
Potato - Potato
3-yr rotations (2 entry pts) - est.1998; Presque Isle, ME
RCB, 4 reps. Plots 30.5 x 3.7 m, ‘Russet Burbank’ potato
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.
Barley/clover
Sweet Corn
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.
Barley/clover-Clover
Soybean-Barley
Green bean-Sweet corn
Sweet corn-Soybean
50
Soybean-Canola
Sweet corn-Canola
Canola-Sweet corn
Potato-Potato
a
ab
b
40
30
cd
20
c
c
c
d
10
0
Fig. 3. Effect of different 3-yr crop rotations on the incidence of
black scurf averaged over 3 field seasons (2001-2004).