Progress Report to the Maine Potato Board Research Subcommittee
January 12, 2007
Project Title: Integration of Crop
Rotations using Barley, Soybean, and Forage Rotation Crops into Potato
Production Systems.
Investigators:
A. Alyokhin, Dept. of Biological Sciences
M.S. Erich, Dept. of Plant, Soil &
Environmental Sciences
E. Gallandt, Dept. of Plant, Soil &
Environmental Sciences
D.H.
Lambert, Dept. of Plant, Soil & Environmental Sciences
Ellen Mallory and Tim Griffin, NEPSWL,
USDA-ARS
G.A. Porter, Dept. of Plant, Soil &
Environmental Sciences (project coordinator)
S. Smith, Dept. of Resource Economics
& Policy
Executive Summary:
A large-scale, cropping system experiment (15 acres, 96 plots) was continued
on Aroostook Research Farm in Presque Isle during the 2006 growing season. This experiment compares soil management
systems, crop rotations, and pest management systems. The soil management systems compared are a conventional,
chemically fertilized system versus an amended system that receives manure and
low rates of chemical fertilizer.
Three crop rotations are compared: 1] two-year standard
(potatoes-barley); 2] four-year intensive (potatoes-soybean-potatoes-barley);
and 3] four-year integrated (potatoes-soybean-barley-alfalfa). An integrated pest management system (IPM)
using conventional chemicals is compared to an environmentally-friendly pest
management system (ENV) that uses fewer and/or less toxic pesticides.
Amended
versus Non-Amended Soils: Soil
analyses show that the amended system has significantly higher soil organic
matter, cation exchange capacity, Modified Morgan available P, and soil-test K,
Mg, and Ca. Soil pH, S, B, and Zn were
also significantly increased by the amendment program and it has also
consistently increased soil aggregation and lowered soil bulk density. These plots have provide a wealth of
information on the use of manure in potato systems and the mineralization of N
from amended potato soils in Maine.
Even though the 2006 growing season had high
rainfall, we saw a 52 cwt/A (18%) yield increase in the amended management
system compared to nonamended. The
incidence of powdery scab root galls was significantly increased in the amended
system, but we have noted much lower incidence in the 4-yr rotation than the
2-yr rotation during the past two years.
The amended system slightly increased scab incidence in the 4-yr
rotation plots, but dramatically increased it in the plots that had potatoes
appearing every other year. Amended
soil management plots had significantly higher specific gravity and slightly
smaller tuber size than conventional soil management during 2006, but otherwise
had comparable tuber quality.
Considering the six-year period from 2001 to 2006, total yields were
higher (27 cwt/A) in the amended soil
management system compared to the non-amended system even though the average N,
P2O5, and K2O fertilizer rates were reduced by
59, 100, and 87%. Soil management
system did not affect incidence early blight, late blight, or rhizoctonia
during 2005, but amendments increased white mold incidence, powdery scab root
gall incidence, and scab incidence on tubers.
The amended soil management system had numerically lower CPB
populations, but significantly greater European corn borer damage and higher
potato aphid populations than the check treatment.
The
amended soil management system, designed to improve soil quality through the
addition of organic amendments, provided the optimal combination of enhancing
potato yields and reducing the year-to-year variability of those yields. Analysis of 1992 - 2004 potato yield data
for this study indicated that potato yields in
the amended soil system (manure, compost, green manure, and supplemental
fertilizer) were equal to or up to 55% higher than yields in the contrasting
nonamended soil system (synthetic fertilizer) in all but one year. Yield stability was also enhanced in the
amended system compared with the nonamended system, as demonstrated by lower
coefficients of variation of total and U.S. #1 potato tuber yield. Stability analysis indicated that yields in
the amended system were less influenced by adverse growing conditions,
particularly low rainfall. Total and
U.S. #1 treatment yields in the poorest yielding year were 65% and 53% of
maximum yields, respectively, in the amended system compared with 44% and 45%
in the nonamended system. Yields and
yield stability were also influenced by pest management system and cultivar,
but not rotation.
Crop
Rotation Comparisons. . The
crop rotation treatments had no significant effects on yield during 2005 and
2006. The four-year rotation tended to
have fewer external tuber defects. We
have also seen very few effects of the rotation treatments on diseases and insects
in this experiment; however, the incidence of powdery scab galls was lower in
the 4-year rotation than in the 2-year rotation during 2005 and 2006. There also tended to be lower incidence of
scabby tubers in the 4-year rotation.
The data show that soybeans can be included in potato rotations with no
short-term yield loss and that short-term potato yields do not strongly benefit
from including forage legumes in the rotation and extending the crop rotation
to one year of potatoes in four. Data from the 2007 through the
2008 growing seasons will provide a more complete picture of the soil, crop,
and pest responses to lengthening a crop rotation to four-years under northern
Maine conditions.
IPM versus an alternative, more
environmentally pest management system (ENV).
Pest
control was very good in the ENV system during 2006 and the results show that
yield and quality were not significantly different in IPM versus ENV pest
management system despite a reduction in the fungicide active ingredient load
compared to the IPM system, the use of biological insect control, and cultural
controls for weed management. Over the
six-year period (2001-2006), we saw no significant yield loss from the ENV pest
management; however, the IPM program had a slight numerical advantage in yield
(14 cwt/A average per year). The
results show that many of the synthetic chemicals used in potato production can
be replaced with other inputs; however, there may be increased in costs (e.g.
CPB control products) and there is the potential for some yield loss (though
not statistically significant in our study).
IPM had significantly higher CPB populations than ENV during 2006. There may be increased risk from alternative
pest management programs in terms of disease spread (e.g. increased virus
disease spread if ENV fails to effectively control aphids; potato aphid
populations were higher in ENV than IPM during 2006 and green peach aphid
populations were significantly higher in ENV during 2005 and numerically higher
in 2006) or disease outbreaks (e.g. although the ENV program has been effective
at controlling early and late blight from 2001 through 2006, we do not know how
it would hold up under heavy disease pressure.
Project Objectives:
1). Continue
a long-term, large-plot, research study focusing on Maine potato cropping
systems by examining:
1a) The
impact of crop rotation length on potato yields, quality, pests and soils.
1b) The
use of soybeans and forages as additional rotation crops in a potato-production
system and their effects on potato yields, quality, pests and soils .
1c) The
impacts of these crop rotations on soil quality with or without additional
organic matter in the form of animal manure.
2). Develop
an understanding of crop performance and potato pest ecology in an IPM-pest
management system compared to a reduced chemical pest management system.
Grant Received:
$7,123
Progress Report for the 2006
Growing Season:
Crop Rotation and Soil
Management Systems: The 2006 field season was the
second field season that we could study the second cycle through our crop
rotation treatments: (crop rotations: barley-potatoes;
barley-potatoes-soybean-potatoes; soybean-barley-forage-potatoes). The data collected from 2001- 2004
represented the system performance in the first full cycle through the
four-year rotation schemes. The data
will be most useful when compared as an average over each four-year cycle (e.g.
the average from 2005 to 2008 would represent the potato performance in the
second full cycle though each four-year rotation).
The 2006 field season represents the
eighth full year in the new soil amendment program. The non-amended soil management system used an average of
170-120-235 lbs/A (N,P2O5 K2O, respectively)
supplied as chemical fertilizer (combined preplant, at-planting, and
sidedressed application). The amended
system averaged 40 tons/A manure (f.w. basis) and received an average of 70-0-0
supplied as chemical fertilizer.
Relative to the non-amended system, the manure application and the past
fertility built up in the amended system resulted in the following reductions
in chemical fertilizer use during 2006: Nitrogen 100 lbs/A (59%), 120 lbs/A P2O5
(100%), and 235 lbs/A K2O (100%).
These plots receive no supplemental
irrigation; however, 2006 was a relatively wet growing season. Despite the high rainfall, there was no
increase in most observed diseases of potato as a result of the alternate soil
and pest management systems. ENV
provided generally good insect pest control and weed control Aphids remained
the major concern for insect control in the ENV system.
Experimental Description
–2006 Potato Cropping Systems Study
15-acre cropping systems
study, 96 plots
Aroostook Research Farm,
Presque Isle, ME
Planted: June 15, 2006
Variety: Atlantic
Vinekilled: September 22, 2006 (99 days after
planting)
Harvested: October 17-19, 2006
Pest Management Systems
IPM vs. BIO (“Environmentally Friendly”)
IPM ENV
“Environmentally Friendly”
Insects higher
thresholds lower thresholds
Provado 1.6F Bt
Monitor Beauveria
bassiana
Fulfill
Disease chlorothalonil azoxystrobin
EDBC and reduced protectant
program
Weeds PE,
metribuzin cultivation -
Lely (75% of plots 1X; 25% of plots 3X)
cultivation (1X) cultivation - between rows (2X)
hilling 2X hilling 2X
Soil Management System
No amendment vs. amended (manure;
reduced fertilizer rate)
Non-amended: 170-120-235 (lbs/A of
N-P2O5 -K2O, respectively).
Amended: 40 tons/A manure (f.w. basis)
70-0-0 supplied as ammonium sulfate. Relative to the non-amended system, the
manure application and the past fertility built up in the amended system
resulted in the following reductions in chemical fertilizer use during 2005:
100 lbs/A (59%), 120 lbs/A P2O5 (100%), and 235 lbs/A K2O
(100%).
Crop Rotations:
IPM System:
1) standard (two-year with grain) potatoes-barley
2) intensive (potatoes 2 out of 4 years plus soybean) potatoes-soybean-potatoes-barley
3) extended (potatoes 1 in 4 years plus soybean and
forage potatoes-soybean-barley-alfalfa
ENV System:
3) extended (potatoes 1 in 4 years plus soybean and
forage potatoes-soybean-barley-alfalfa
History:
1991-1998 Old Design last
full report published covered 1991-1994
last journal paper
covered up to 1996
New Design:
1998 new design rotation crops planted
1999 transition year, second year of new standard,
intensive, and extended rotations
2000 transition year, third year of new standard, intensive, and extended
rotations
2001-2004 first complete cycle of intensive and
extended rotations
each year generates a full set of data comparing
crop rotations
four-year averages are
the most appropriate measure of rotation performance
2005-2008 second complete cycle of intensive and
extended rotations
each year generates a full set of data comparing
crop rotations
four-year averages are
the most appropriate measure of rotation performance
Soils: The comparison of the amended versus non-amended management
systems allows us to determine how an “organic matter rich” system will respond
compared to a conventional, short-rotation, fertilizer-based soil management
system. The non-amended system is
typical of that used on most commercial farms in the area. It is our reference or standard system. The amended system has received “long-term”
applications of manure and/or compost (since 1991) and low rates of chemical
fertilizer. This system might be
typical of one used in future “sustainable” programs, organic production, or
conventional farming integrated with animal-based agriculture. Percent organic matter in the amended system
is approximately 4.8% compared to 2.8% in the conventional system. The amended system has significantly higher
soil organic matter, cation exchange capacity, Modified Morgan available P, and
soil-test K, Mg, and Ca. Soil pH, S, B,
and Zn were also significantly increased by the amendment program. We have also consistently seen greater soil
aggregation and lower soil bulk density in the amended system. Soil moisture levels are typically higher
early in the season and after rainfall events
A laboratory study was
completed exploring how soil amendment history affects the transformation and
availability of recently added N. Net mineralization in the historically amended soil
was twice that in the nonamended soil, mostly due to differences in soil total
N stocks. When N sources were added, NH4+
consumption, net N mineralization, and estimated N pools were affected by both
soil amendment history and N source, with a significant interaction between the
two factors. Historically amended soil
reduced the availability of recently added N relative to the nonamended
soil. This reduction occurred in the
active pool (N1) for
the high C/N manure and in the slow pool (N2) for fertilizer.
It appeared to be related to the timing of C availability. Future work modeling N availability should
consider soil amendment history not only for its effects on soil N supply
capacity, but also for its effects on the availability of recently added N
sources. The results of this study are
in press with the Soil Science Society of America Journal.
We
also studied the relative contribution of current versus previous applications
of manure nitrogen to a barley crop. Barley samples were collected at physiological
maturity from historically amended and nonamended plots where manure or
fertilizer had been applied as usual and in subplots where these N applications
had been withheld. The samples were
analyzed for N content, or N uptake.
The data from the different subplots were used to estimate what
proportion of the available N came from current versus previous application of
manure. It was found that
mineralization of residual organic N from previous manure applications
contributes more N to a current crop than is typically credited in nutrient
management planning.
Potato Crop: We
measured plant emergence, stands, and percent ground cover during the growing
season. Petiole samples, leaf samples,
foliage samples, and tuber samples were collected for nutrient analysis. The crop was harvested, weighed and graded
to measure yield and tuber quality.
Potato tubers were placed in storage and the incidence of superficial
tuber diseases was measured.
Results: Summary yield and quality data from 2006 are presented in Table
1. Even though the 2006 growing season
had high rainfall, we saw a 52 cwt/A (18%) yield increase in the amended
management system compared to nonamended.
The incidence of powdery scab root galls was significantly increased in
the amended system, but we have noted much lower incidence in the 4-yr rotation
during the past two years (Figure 1).
The amended system slightly increased scab incidence in the 4-yr
rotation plots, but dramatically increased it in the plots that had potatoes
appearing every other year (Table 1; Figure 2). Amended soil management plots had significantly higher specific
gravity and slightly smaller tuber size than conventional soil management
during 2006, but otherwise had comparable tuber quality. Considering the six-year period from 2001 to
2006, total yields were higher (27
cwt/A) in the amended soil management system compared to the non-amended
system even though the average N, P2O5, and K2O
fertilizer rates were reduced by 59, 100, and 87%. These data show that manure and soil nutrient reserves can
effectively replace fertilizer nutrients and that potato yields can be
increased by the use of organic soil amendments even when low chemical
fertilizer rates are used. The data also
show that the yield benefits from the use of soil amendments are greater during
dry years (e.g. 2001) than wetter years (e.g. 2003, 2004, and 2005). This differential effect reflects higher
soil organic matter content, improved soil structure, and greater water holding
capacity.
The crop rotation treatments
had no significant effects on yield and tuber quality during 2006 (Table 3),
but there was a trend toward lower incidence of external tuber defects such as
scab (Table 1; Figure 2). These data show
that soybeans can be included in potato rotations with no short-term yield
loss. The data also suggest that potato
yields do not benefit in the short-term from extending the crop rotation to one
year of potatoes in four and including forage legumes in the rotation. This is surprising, since we expected and
have seen in other experiments that less frequent potato production can reduce
pest incidence and improve soil physical properties. The lack of rotation effect in this experiment may be due to the
relatively short duration of the rotation treatments or the predominance of wet
growing seasons in recent years. We’d
expect more benefits from soil improving strategies during drier years.
Pest control was very good
in the ENV system during 2006 and the results show that yield and quality were
not significantly different in IPM versus ENV pest management system despite a
reduction in the fungicide active ingredient load compared to the IPM system,
the use of biological insect control, and cultural controls for weed management
(Table 1). Over the six-year period
(2001-2006), we saw no significant yield loss from the ENV pest management;
however, the IPM program had a slight numerical advantage in yield (14 cwt/A
average per year). The results show that
many of the synthetic chemicals used in potato production can be replaced with
other inputs; however, there may be increased in costs (e.g. CPB control
products) and there is the potential for some yield loss (though not
statistically significant in our study).
There also may be increased risk from alternative pest management
programs in terms of disease spread (e.g. increased virus disease spread if ENV
fails to effectively control aphids; green peach aphid populations were higher
in ENV than IPM during 2005 and 2006) or disease outbreaks (e.g. although the
ENV program has been effective at controlling early and late blight from 2001
through 2006, we do not know how it would hold up under heavy disease
pressure). If these changes in pest
management practices are to occur, growers would need to receive a higher price
for their efforts or other programs would need to be enacted to foster riskier,
but more environmentally benign approaches.
Table 1. Potato
yield and quality as affected by pest management, soil amendment, and crop
rotation. Potato Ecosystem Project,
Aroostook Research Farm, Presque Isle, ME.
2006 Growing Season.
Yield (cwt/A) % Ext. Defs. Size
Distribution (%) Spec.
Total US#1 US#1 Total
Scab 1f 2¼ 2½
Grav.
>2¼
" to
4" to 4" to 4"
Pest Management System
Comparison:
IPM pest mgt. 315 264 239 14.0 2.7
96.9 87.9 61.2 1.095
ENV pest mgt. 299 253 227 12.0 1.2
96.3 86.0 60.8 1.095
No Amendment 279 234 211 14.2 0.2
97.5 87.6 61.3 1.092
Amended 337 286 258 11.4 3.8
95.5 86.1 60.7 1.098
AOV
Results:
Pest
Mgt. .13 ns ns ns
ns ns ns ns ns
Soil
Mgt. * .09 .12 ns .06 .09 ns ns .07
Pest.
x Soil ns ns ns ns ns ns ns ns ns
Soil Management within
the IPM System:
No Amendment 301 258 234 12.5 1.0
97.8 88.6 63.2 1.091
Amended 347 257 226 23.9 16.6
96.2 85.1 59.4 1.096
Two-year Rotation1 326 256 226 20.4 12.6
97.3 86.5 61.8 1.092
Four-yr intensive Rotation2 327
253 226 19.1 9.6
96.9 86.5 61.1
1.094
Four-year Rotation3 315 264 239 14.0 2.7
96.9 87.9 61.2 1.095
AOV
Results:
Soil
Mgt. * ns ns .12
* ** * ns *
Rotation ns ns ns
ns ns ns ns ns ns
Rot.
x Soil ns ns ns
ns ns * ns ns ns
External defects in the pest management
sequence: growth cracked tubers were the most prevalent defects. External defects in the soil management
sequence: scabby and growth cracked tubers were the most prevalent defects.
1 Barley-Potato Rotation (in place since 1991 growing season)
2 Barley-Potato-Soybean-Potato
(started in 1999, 2006 data are the second cycle through this rotation).
3 Soybean-Barley-Forage-Potato (started in 1999, 2006 data are the
second cycle through this rotation).
Note: due to problems in the field, plot 323
was dropped from the analysis.
Potato Yields and Yield
Stability. The amended soil management system, designed to
improve soil quality through the addition of organic amendments, provided the
optimal combination of enhancing potato yields and reducing the year-to-year
variability of those yields. Analysis
of 1992 - 2004 potato yield data for this study indicated that potato yields in the amended soil system (manure, compost,
green manure, and supplemental fertilizer) were equal to or up to 55% higher
than yields in the contrasting nonamended soil system (synthetic fertilizer) in
all but one year. Yield stability was
also enhanced in the amended system compared with the nonamended system, as
demonstrated by lower coefficients of variation of total and U.S. #1 potato
tuber yield. Stability analysis
indicated that yields in the amended system were less influenced by adverse
growing conditions, particularly low rainfall.
Total and U.S. #1 treatment yields in the poorest yielding year were 65%
and 53% of maximum yields, respectively, in the amended system compared with
44% and 45% in the nonamended system.
Yields and yield stability were also influenced by pest management
system and cultivar, but not rotation.
The results of this study are
being published in Agronomy Journal.
Potato
Disease Management: From 1995-98, disease management in the BIO system was based
on frequent application of Cu-containing compounds. This provided a comparison versus standard synthetic fungicides. The program was successful in that we had
few problems with the major foliar diseases on potato, late blight and early
blight. Unfortunately, the BIO system
tended to be associated with earlier crop senescence and significant reductions
in crop yields during most years from 1991-1998. The result was a system that was not economically viable in our
analysis of short-term returns.
Because of the significant yield loss commonly observed in the BIO
system from 1991-98 and because we felt that a disease management program so
heavily based on a persistent metal (Cu) was undesirable, we modified the BIO
system into an “environmentally-friendly” system, synthetic-chemical-based
system (ENV) and have used that system since 1999. Disease management in the ENV program uses minimal rates and
frequencies of chlorothalonil and strobilurins with application frequencies
dependent on disease pressure forecasts.
This program is similar to that developed in Wisconsin in conjunction
with the World Wildlife Fund. The ENV pest management system has been very effective
is providing disease control, while reducing the fungicide input in a period
when disease pressure has been low.
Active ingredient applications have typically been reduced by 60% in
each growing season.
The two diseases that the fungicide treatments are designed to
control are late blight (Phytophthora)
and early blight (Alternaria). Late blight has been absent or sporadic in
the plots since 1998, and incidence of foliar early blight has been low to
negligible. Several other important
diseases affected by the Cropping System treatments are present in the
study. These include white mold (Sclerotinia), powdery scab (Spongospora) / Potato Mop-Top Virus
(PMTV), and Rhizoctonia.
White Mold - White mold was
sufficiently evident to warrant rating in 1997, 2000, 2003 and 2006. In 2000, when disease pressure was high,
incidence in the environmentally friendly plots was one third that in the IPM
plots. To some degree, this was
attributed to the use of Quadris, a strobilurin fungicide labeled for white
mold on other crops. Over the 10-year
period, white mold incidence in the amended plots has increased relative to the
nonamended plots. This difference
became statistically significant in 2006. Presumably, the generally damper
soils in the amended plots marginally favor the disease in any year and the
disparity increases over time as inoculum differences compound. Neither the previous crop sequence, rotation
length (2 or 4 yr), or pest management treatment were statistically significant
in 2006.
The two diseases that the
fungicide treatments are designed to control are late blight (Phytophthora) and early blight (Alternaria). Late blight has been absent or sporadic in the plots since 1998,
and incidence of foliar early blight has been low to negligible. Several other important diseases affected by
the Cropping System treatments are present in the study. These include white mold (Sclerotinia), powdery scab (Spongospora) / Potato Mop-Top Virus
(PMTV), and Rhizoctonia.
White Mold - White mold was
sufficiently evident to warrant rating in 1997, 2000, 2003 and 2006. In 2000, when disease pressure was high,
incidence in the environmentally friendly plots was one third that in the IPM
plots. To some degree, this was
attributed to the use of Quadris, a strobilurin fungicide labeled for white
mold on other crops. Over the 10-year
period, white mold incidence in the amended plots has increased relative to the
nonamended plots. This difference
became statistically significant in 2006 (Table 2). Presumably, the generally
damper soils in the amended plots marginally favor the disease in any year and
the disparity increases over time as inoculum differences compound. Neither the previous crop sequence, rotation
length (2 or 4 yr), or pest management treatment were statistically significant
in 2006.
Table 2. Incidencea
of white mold in relation to soil amendment
and pest treatment.
___________________________________________________________________
Soil treatment Pest treatment
---------------------------- -----------------------------
Year Non Amnd IPMc ENV
___________________________________________________________________
1997 2 2 1 3
* c
2000 13
18 20 6 ***
2003 10 19 16 13
2006 13 24* 17 24
____________________________________________________________________________________
a 2000 rating system = numbers of infections per row within
two-plant observation units; 2003 and 2006
= numbers / 30
observations.
b Amnd = amended, Non = nonamended; IPM = “conventional” and
“reduced input” in 1997, and “IPM” in 2000 - 2006, Env = “biological” in 1997
and “environmentally friendly” in 2000 - 2006.
c Statistically significant within the same year at P = 0.05 (*) or
P = 0.001 (***).
Powdery Scab / PMTV - Two
patterns of powdery scab incidence and severity have emerged in the Cropping
System’s plots. This disease is quite
sensitive to periods of high soil moisture which allow spore dispersal in
conjunction with tuber susceptibility, and severity varies considerably from
year to year despite the general availability of inoculum every year. In years when the disease has been monitored
by root or tuber symptoms, incidence in the amended plots has been at least
4-fold that in the nonamended plots (Table 3). Incidence in the environmentally-friendly plots has been
substantially lower than that for the conventional/reduced input/IPM plots in
several years. While the possibility
that powdery scab inoculum was introduced with the potato compost or manure
amendments exists, differences in soil moisture are a more consistent
explanation of the greater disease in the amended plots. Regression analysis of powdery scab incidence
data from past years indicates that scab severity increases with higher soil
organic matter levels and with the associated higher water content. This pattern appears sufficiently strong to
explain the differences in powdery scab incidence between the amended and
nonamended treatments. The previous heavy applications of copper to the
biological plots are a likely explanation of less disease in these plots. Powdery scab has been higher in 2-year
rotations than in 4-year rotations, significantly so in the last two
years.
In 2002, 3/16 amended plots were positive for mop-top virus;
in 2003 1/16 amended plots was positive.
In 2005, PMTV was detected in a single amended) plot in which 7 of 9
plants were positive. In 2006 PMTV was detected in one amended plot (2/6 hills)
and one nonamended plot (1/6 hills).
Table 3. Percentage powdery
scab tuber 1996) and root gall incidence (2000-2006) as affected by soil, pest,
and rotation treatments.
______________________________________________________________________________
Soil amendment Pest
treatmentb Rotation
Year Non Amnd IPM ENV 2-yr
4-yr
-----------------------------------------------------------------------------------------------------------------
1996 - Superior
0.1 0.9***c 0.7 0.2***
1996 - Atlantic 2 17 *** 13 3 ***
2000 - Atlantic 8 55
*** 35 20 33 30
2001 - Atlantic 3 15
*** 12 0
* 11 10
2002 - Atlantic
23 62 ** 34
33