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Title: Effect of tillage and vetch-corn versus vetch-grain sorghum succession multicropping systems on population dynamics of phytoparastic nematodes
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Permanent Link: http://ufdc.ufl.edu/UF00056092/00001
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Title: Effect of tillage and vetch-corn versus vetch-grain sorghum succession multicropping systems on population dynamics of phytoparastic nematodes
Series Title: Agronomy research report
Physical Description: 8 leaves : ; 28 cm.
Language: English
Creator: Corella Vargas, Josâe Francisco, 1957-
Gallaher, Raymond N
Dickson, Donald W ( Donald Ward )
University of Florida -- Agronomy Dept
Publisher: Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1988?]
 Subjects
Subject: Corn -- Diseases and pests -- Florida   ( lcsh )
Sorghum -- Diseases and pests -- Florida   ( lcsh )
Cropping systems -- Florida   ( lcsh )
Tillage -- Florida   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaves 5-6).
Statement of Responsibility: J.F. Corella, R. N. Gallaher and D.W. Dickson.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00056092
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 62615394

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




]00

/ 6-
^g-o I Librar
Agronomy Research Report, AY-88-01 'FGB 2 99(
Effect of Tillage and Vetch-Corn Versus Vetch-Grain.Sorghum-Succession
Multicropping Systems on Population Dynamics of Phytbparast'c'Nematodes.

J. F. Corella, R. N. Gallaher, and D. W. Dickson
Graduate Research Assistant (Former Federal Research Scientist, M4G, Costa Rica),
Professor of Agronomy, and Professor of Nematology, Institute of Food and
Agricultural Sciences, Departments of Agronomy and Entomology and Nematology,
University of Florida, Gainesville; FL 32611.

ABSTRACT
The effect of two cropping and tillage systems on the population dynamics of
four nematode species was evaluated on a loamy sand (Grossarenic Paleudult).
'Hairy' vetch (Vicia villosa) succeeded by corn (Zea mays) or grain sorghum
(Sorghum bicolor7 ere seeded in split plots randomizedwithin whole plots of
no-tillage versus conventional tillage over four growing seasons (1980-1983). The
vetch-corn cropping system increased the root-knot nematode (Meloidogyne
incognita) population by 290% compared to the vetch-grain sorghum cropping
system. In contrast, the vetch-grain sorghum cropping system increased ring
nematode (Criconemella ornata) populations by 65% compared to the vetch-corn
cropping system. Root-knot and ring nematodes were affected more by these
cropping systems than were lesion (Pratylenchus brachyurus) or stubby-root
(Paratrichodorus minor) nematodes. Multiple cropping systems, vetch varieties
and crop host preference affected nematode populations, whereas conventional or
no-tillage treatments had little effect on them.


Minimum tillage and double-cropping systems are being adopted rapidly by the
agricultural community in the United States. Minimum-tillage is described as
"planting directly into an unprepared seedbed and the elimination of tillage
operations through harvest," whereas, multiple-cropping is defined as "growing
two or more crops the same year on the same land area" (6).
The increasing use of minimum-tillage and double-cropping in the
southeastern United States necessitates a better understanding of their effects
on soil populations of phytoparasitic nematodes. Several authors have reported
nematode population increases on crops in the field with corresponding reductions
in yields, but few have related the effect of tillage systems on soil densities
of phytoparasitic nematodes (1,5,9-11). Thomas (16) examined the population
densities of several phytoparasitic nematodes under seven tillage regimes. He
reported that different tillage systems resulted in numerical differences among
nematodes, with numbers generally being greatest in the no-tillage plots and
lowest in fall-or spring-plowed plots. Similar results were obtained by Caveness
(2), when Meloidogyne incognita (Kofoid and White) Chitwood populations were
monitored in corn (Zea mays L.) grown with conventional tillage and no-tillage
management. In the same study, however, populations of Pratylenchus sp. were
greater in tilled soils. Stinner and Crossley (15) noted more phytoparasitic
nematodes in grain sorghum (Sorghum bicolor L. Moench) grown under no-tillage
than under conventional tillage. Rich et al. (13) reported subsoiling corn
caused an increase in M. incognita and Criconemella spp. populations, but numbers
of Pratylenchus zeae Graham were not affected. Subsoiling generally resulted in a
change in distribution of corn roots and nematodes in the soil profile, but









caused little total increase in either roots or numbers of nematodes. Corn yield
was increased by subsoiling.
Johnson (8) reported that root-knot nematode populations can be manipulated
by intensive cropping systems and by crops within each system. Dunn (3) reported
that when crops are grown in close sequence in the same field, nematodes that
build up on the first crop may be important to the success of the second crop.
Severe damage to the second crop is 'likely if the two crops in the sequence are
susceptible to damage by root-knot, sting or stubby-root nematodes. These
nematodes will increase on corn and severely damage a succeeding crop such as
sorghum.
The incorporation of resistance into crops to individual Meloidgyne spp. has
been successful in a number of vegetables and field crops; but, relatively little
work has been undertaken in forage legumes. The interest in forage legumes has
been renewed because of the increased cost of fertilizers and the demand for high
quality forage. Most of the research in forage legumes has been carried out on
Trifolium spp., Medicago satava L. and tropical forage legumes (12). Vetch
(Vicia villosa Roth) has also received limited attention in nematode breeding
programs (Pers. comm. ).
The objectives of this study were to determine the effect of long-term
double cropping systems and tillage management on the dynamics of phytoparasitic
nematodes.

MATERIALS AND METHODS
Vetch ('Hairy') succeeded by corn or grain sorghum were grown in split plots
randomized within whole plots of no-tillage versus conventional tillage over five
growing seasons (1979-1983). Treatments with and without subsoiling were
Included in both tillage systems. Treatments were replicated four times. Each-
plot was 7.6 m long and 13.7 m wide. From 1979 to 1981 the cropping systems
included vetch succeeded by corn or vetch succeeded by grain sorghum. In 1981
tillage plots were split again with vetch cultivars as the split-split plot
treatment. Cultivars included: vetch 'Hairy', 'Vantage', 'Cahaoba',
'Vanguard', and 'Nova II'; corn 'DeKalb XL71'; sorghum 'DeKalb BR64'. The
latter four cultivars of vetch reportedly had "root-knot nematode" resistance.
In 1982 and 1983 plots previously planted to corn or sorghum were split between
corn and sorghum.
The soil was an Arredondo loamy sand (loamy siliceous, hyperthermic,
Grossarenic Paleudult). Hairy vetch, used as a cover crop, was killed with
paraquat jl,1'-dimethyl-4,4'-bipyridinium dichloride) applied at a rate of 1
liter ha in late March or early lpril. Each year in the fall the plots were
harrowed three times and 33 kg ha of hairy vetch were planted with a drill in
rows spaced 0.18 m apart, The vetch was topdressed with 20-16-85-4-2 kg ha of
N-P-K-Mg-S plus 5 kg ha- Frit 503 trace elements.
Conventional tillage for the succeeding grain sorghum or corn consisted of
two rototill passes before planting. Grain sorghum and corn were planted
directly into the killed vetch for no-tillage treatments or into the conventional
tilled plots in 0.75 m wide rows with and without subsoiling using a two-row
Brown-Harden Super-Seeder (Brown Mfg. Co., Banks, AL). In a single operate on the
following treatments were performed: corn was seeded at 60,000-seeds ha ; 673
kg ha of 5-10-15 (N-P-K) was banded over the row; a tank mix application of
herbicides consisted of 0.42 kg a.i.ha" paraquat plus 425 ml ha" of Ortho X-77
surfactant plus 2.8 kg a.i. ha" of linuron (Lasso)
(3-(3,4-dichlorophenyl)-l-methoxy-l-methyl-urea) and 2.2 kg a.i. ha-1 of atrazine
(2-chloro-4-ethylamino-6-isopropyl-amino-1,3,5-triazine).









Grain sorghum was planted to obtain a plant population of about 370,500
plants ha-1. Fertilizer and paraquat applications were the same as for corn
When the sorghum was about 0.12 m tall a post application of 2.2 kg a.i. ha-
atrazine was broadcast over the sorghum.
Both corn and grain sorghum received at least one application of post
directed herbicides: (1.12 kg a.i. ha- ametryn (Evik)
(2-(ethylamino)-4-(isopropyl amino)-.-(methylthio)-s-triazine), and 0.56 kg a.i.
ha- 2,4-D (2,4-dichlorophenoxyacetic acid) for additional weed control when
plants were about 0.5 m tall.
Soil samples for nematode assay were taken two to four times each year when
the crop was at or near harvest. The center rows of each plot were sampled in
the crop root rhizosphere 0.15 m deep with a cone-shaped sampling tube
(2.5-cm-diameter). A sample consisted of 20 cores composite from each plot.
Samples were placed in 0.5-mil plastic bags and stored at 10 C until processed 2
to 5 days after sampling. The soil was mixed and 250-cnr of each sample was
processed by a sugar-flotation-centrifugation method (7). Root samples,
consisting of bulked roots from five or more plants selected at random from each
plot, were assayed (4). Nematodes were counted and identified to species. Roots
of 20 plants were taken from each plot to rate root-knot nematode. Root-gall
ratings were based on the following scale: 0 = no galls; 1 = 1-2; 2 = 3-10; 3 =
11-30; 4 = 31 100; and 5 = > 100 galls per root system (14).

RESULTS

The mean population densities of M. incognita averaged over four years were
higher under vetch-corn double cropping (290% greater) than under the vetch-grain
sorghum double cropping system (Table 1). This nematode was not influenced by
tillage treatment (no-tillage, no-tillage plus subsoiling, conventional tillage
and conventional tillage plus subsoiling). In contrast, the vetch-grain sorghum
double cropping system increased the mean population densities of C. ornata by
65% compared to the vetch-corn double cropping system. The numbers of P. minor
and Pratylenchus brachyurus (Goefrey) Filipjev and Schuurmans-Stekhovenf'rom soil
were not influenced by either cropping system or tillage system; however, the
mean number of lesion nematodes recovered from roots was higher under the
vetch-corn cropping system than the vetch-grain sorghum cropping system (Table
1). There was a higher root-knot nematode galling index under vetch-corn double
cropping than vetch-grain sorghum double cropping. Tillage treatments did not
influence the galling index.
The mean population densities of nematodes were also affected by the
individual crop species grown in the two cropping systems (Table 2). Populations
of M. incognita were higher when corn was growing in the field compared to grain
sorghum. Populations of C. ornata were higher under grain sorghum than corn.
Populations of P. minor and P. brachyurus populations were not influenced by the
crop species (Table 27. Vetch had lower root-gall index values when it was
proceeded by sorghum than when it was preceded by corn. Corn had a higher
root-gall index than sorghum. The mean number of P. brachyurus was higher in
vetch roots when it succeeded corn compared to grai-n sorghum. The number of P.
brachyurus in grain sorghum or corn roots were not different (Table 2).
When previously planted corn or grain sorghum plots were split between corn
and grain sorghum, the mean number of M. incognita were higher in the
corn-vetch-corn cropping system (178 and 156) than in the corn-vetch-grain
sorghum or the sorghum-vetch-corn system. The mean number of M. incognita in the
corn-vetch-corn cropping system were 611% higher than the sorghum-vetch-sorghum
cropping system. The mean number of M. incognita in the corn-vetch-grain sorghum









and sorghum-vetch-corn systems each had a 156 and 178% higher population density
of M. incognita than in the sorghum-vetch-sorghum cropping sequence (Table 3).
The mean number of C. ornata was highest with the sequence sorghum-vetch-sorghum
compared to the other cropping sequences. The corn-vetch-corn sequence had the
lowest mean number of C. ornata. Pratylenchus brachyurus had a higher mean number
in the corn-vetch-corn and corn-vetch-sorghum than in the sorghum-vetch-corn and
the sorghum-vetch-sorghum sequences.' Paratrichodorus minor did not show any
significant responses in any of the sequences tested.
A significant response in the populations of two nematodes was caused by
tillage treatments only during two sampling dates. No-tillage had higher total
nematodes at both of these dates (average of 92 and 49 total nematodes per 250
cnr of soil for no-tillage and conventional tillage, respectively). The M.
incognita population showed slight differences, but C. ornata had the greatest
difference in populations between tillage treatments and were highest in the
no-tillage treatment. Numbers of P. minor and P. brachyurus did not differ among
tillage treatments.
The effect of tillage treatment on nematode population densities was
different depending on the cropping system. The vetch-grain sorghum cropping
system had a larger difference in total nematode population compared to the
vetch-corn cropping system. This was attributed to the higher population of ring
nematodes in the vetch-grain sorghum cropping system. Both planting dates in
which nematodes responded to tillage were when hairy vetch was growing in the
field and the proceeding nematode counts were the highest found among all
sampling dates.
Hairy vetch was more susceptible to M. incognita than other vetch cultivars
(Table 4). Very few root-knot nematode galls were found on the four nematode
resistant cultivars. Vanguard and Cahaoba had the highest number of lesion
nematodes per 10 g of roots. Yantage, Cahaoba, and Vanguard supported a higher
population of C. ornata compared to Hairy and Nova II. The mean number of P.
brachyurus and-P. m-nor from soil did not show any differences among cultivars.
The root-gall index was highest for Hairy vetch among the five cultivars in
the vetch-corn cropping system compared to the vetch-grain sorghum cropping
system (Table 5); however, this cultivar had the lowest number of root-knot
nematodes per 10 g of roots when grown in the vetch-corn cropping system.
Vanguard and Nova II had the highest numbers of root-knot nematodes per 10 g of
roots in the vetch-sorghum cropping system.

DISCUSSION

Meloidogyne incognita was mainly affected by cropping system and the host
crop. The population levels of this nematode were higher with the vetch-corn
abuble cropping system. The nematode reached its highest populations when corn
was growing in the field. The vetch-grain sorghum double cropping system caused
a reduction in populations of M. incognita compared to vetch-corn double
cropping. Grain sorghum depressed the mean number of M. incognita and the
nematode density was the lowest when grain sorghum was succeeded by vetch-grain
sorghum. The root-gall index was higher in the vetch-corn cropping system
compared to the vetch-grain sorghum system. Vetch had the lowest root-gall index
when it was growing in the field in the vetch-grain sorghum system. On the other
hand corn had the highest root-gall index when it was growing in the field in the
vetch-corn system.
The population density of C. ornata in the vetch-grain sorghum cropping
system was higher than in the veTch-corn cropping system. The C. ornata
population increased each time grain sorghum was involved in the cropping









sequence.
Soil populations of P. brachyurus and P. minor were not affected by cropping
systems or crop species; 7iwever, P. brachyurus populations in the roots were
higher in the cropping system vetcn-corn compared to vetch-grain sorghum. When
corn proceeded vetch, the number of P. brachyurus in roots were higher in vetch
than when vetch was proceeded by sorgEum.
When one is attempting to suppress root-knot nematodes grain sorghum is a
better crop than corn for succession double cropping with vetch when moderate to
high populations of M. incognita are present; however, when C. ornata is present
in high populations and root-knot nematodes are absent the vetch-corn double
cropping sequence would be best.
Only two of 18 sampling dates showed a significant response in the
populations of nematodes due to tillage. Ring nematode was affected by tillage
management more than the other nematodes and this nematode was highest in
no-tillage plots compared to conventional tillage plots.

LITERATURE CITED
1. Barker, K. R., and T. H. A. Olthof. 1976. Relationships between nematode
population densities and crop responses. Annual Review of Phytopathology
14:327-353.
2. Caveness, F. E. 1974. Plant-parasitic nematode population differences
under no-tillage and tillage soil regimes in western Nigeria. Journal of
Nematology 6:138 (Abstr.).
3. Dunn, R. A. 1980. Ways nematodes complicate management of multiple
cropping systems. Florida Cooperative Extension Service. Institute of Food and
Agricultural Sciences. University of Florida, Gainesville. Multiple Cropping
Minimum Tillage, W4T-14.
4. Endo, B. Y. 1959. Responses of root-lesion nematodes, Pratylenchus
brachyurus and P. zeae, to various plants and soil types. Phytopathology
49:417-421.
5. Fortnum, B. A., and D. L. Karlen. 1985. Effect of tillage system and
irrigation on population densities of plant nematodes in field corn. Journal of
Nematology 17:25-28.
6. Gallaher, R.N. 1980. Multiple-cropping, minimum-tillage. Florida
Cooperative Extension Service. Institute of Food and Agricultural Sciences,
University of Florida, Gainesville. Multiple Cropping Minimum Tillage, MIT-01.
7. Jenkins, W. R. 1964. A rapid centrifugal-flotation technique for
separating nematodes from soil. Plant Disease Reporter 48:692.
8. Johnson, A. W. 1985. Specific crop rotation effects combined with
cultural practices and nematicides. Pp. 283-301 in J. N. Sasser and C. C. Carter,
eds. An Advanced Treatise on Meloidogyne: Biology and Control, vol. I. Raleigh,
North Carolina State University Graphics.
9. Minton, N. A., and M. B. Parker. 1987. Root-knot nematode management and
yield of soybean as affected by winter cover crops, tillage systems, and
nematicides. Journal of Nematology. 19:38-43.
10. Mitchell, D. J., N. C. Schenk, D. W. Dickson, and R. N. Gallaher. 1980.
The influence of minimum tillage on populations of soilborne fungi,
endomycorrhizal fungi and nematodes in oat and vetch. Pp. 115-119 in R. N.
Gallaher, ed. Proceedings of the Third Annual No-Tillage Systems
Conference. Institute of Food and Agricultural Sciences, University of Florida.
11. Norton, D. C., J. Tollefson, P. Hinz, and S. H. Thomas. 1978. Corn
yield increases relative to nonfumigant chemical control of nematodes. Journal of
Nematology 10:160-166.









12. Quesenberry, K. H., D. D. Baltensperger, and R. A. Dunn. 1986.
Screening Trifolium spp. for response to Meloidogyne spp. Crop Science 26:61-64.
13. Rich, J. R., C. Hodge, and W. K. Robertson. 1986. Distribution of field
corn roots and parasitic nematodes in subsoiled and nonsubsoiled soil. Journal of
Nematology 18:203-207.
14. Taylor, A. L., and J. N. Sasser. 1978. Biology, identification and
control of root-knot nematodes (Meloidogyne species). Cooperative Publication,
Department of Plant Pathology, North Carolina State University, and U. S. Agency
of International Development, Raleigh.
15. Stinner, B. R., and D. A. -Crossley, Jr. 1982. Nematodes in no-tillage
agroecosystems. Pp. 14-28 in D. W. Freckman, ed. Nematodes in Soil Ecosystems.
Austin: University of Texas Press.
16. Thomas, S. H. 1978. Population densities of nematodes under seven
tillage regimes. Journal of Nematology 10:24-27.




Table 1. Population densities of four phytoparasitic nematodes and root-gall index from two
multiple-cropping systems averaged over four years in a loamy sand soil of Florida.
Mean no. nematodes per 250 cm3 soil
R oot-gall Lesion per
Cropping system Root-knot Ring Lesion Stubby-root index 10 g roots

Vetch-corn 82 130 28 NS 51 NS 3.3 231 *
Vetch-grain sorghum 21 215 24 48 1.5 123


Root-knot = Meloidogyne incognita, Ring = Crioconemella ornata, Lesion = Pratylenchus
brachyurus stubby-root = Paratrichodurus minor.
Root-gall index: 0 = no galing, 1 = I 2, 2 = 3 10, 3 = 11 30, 4 = 31 100, 5 = > 100 galls
per plant.
= Significant difference between systems according to F test (P = 0.05). NS = No significant
differences
1/. Each mean for nematodes in sail is an average of 4 replications X 4 tillage treatments X 13
dates. Each mean for root-gall index and lesion nematodes per 10 g roots is an average or 4
replications X 4 Tillage X 8 sampling dates.









Table 2. Effect of individual crops in two cropping systems on the population densities of four
phytoparasitic nematodes, and root-gall index in a loamy sand soil of Florida.
Mean no. nematodes per 250 cm3 soil
Cropping Crop in Root-gall Lesion per
system the field Root-knot Ring L'eson Stubby-root index 10 g roots


Vetch-corn vetch 17 1/ 190 '33 NS 40 NS 3.1 a 2/ 326 a
corn 151 134 43 38 3.6 a 158 a

Vetch-sorg. vetch 8 263 23 NS 25 NS 0.8 b 81 b
sorg. 41 242 29 29 2.9 a 155 a

Root-knot = Meloidogyne incognita, Ring = Crioconemella orata, Lesion = Pratylenchus
brachyurus stubby-root = Paratrichodurus minor.
Root-gall index: 0 = no galling, = 1 2, 2 = 3 10, 3 = 11 30, 4 = 31 100, 5 = > 100 galls
per plant.
1/. = Significant differences between crops within a single cropping system in columns for
nemaTodes in soil according to F test (P = 0.05) NS = No significant differences. Each mean is an
average of 4 replications X 4 tillage treatments X 13 sampling dates.
2/. Data in columns for root-gall index and lesion nematodes per 10 g roots followed by the same
letter are not significantly different according to Duncan's new multiple range test (P = 0.05) Each
mean is an average of 4 replications X 4 tillage treatments X 8 sampling dates.


Table 3. Population densities of four phytoparasitic nematodes
following reversal of vetch-corn and vetch-grain sorghum double cropping
in a loamy sand soil of Florida.
Mean no. of nematodes per 250 cm3 soil

Cropping system Root-knot Ring Lesion Stubby-root

Corn-vetch-corn 128 a 155 d 32 a 8 a
Corn-vetch-sorghum 46 b 230 c 40 a 8 a
Sorghum-vetch-corn 50 b 290 b 9 b 10 a
Sorghum-vetch-sorghum 18 c 334 a 14 b 8 a

Root-knot = Meloldogyne incognita, Ring = Criconemella omata,
Lesion = Pratylenchus brachyurus Stubby-root = Paratrichodorus minor.
Data in columns followed by the same letter are not significantly
different according to Duncan's new multiple range test (P = 0.05) All
means are an average of 4 replications X 4 tillage treatments X 2
sampling dates.








Table 4. Mean number of four phytoparasitic nematodes and root-gall index
cultivars of vetch in a loamy sand soil of Florida.


affected by five


Mean no. per 250 cm3 soil
Vetch R oot-gall Lesion per
cultivar Root-knot Ring Lesion Stubby-root index 10 g roots


Hairy 77 a 124 b 13 a 57 a 2.1 a 6.6 b
Yantage 3 b 187 a 14 a 89 a 0.1 b 10.3 b
Cahaoba 3 b 158 a 14 a 91 a 0.0 b 27.0 a
Vanguard 7 b 193 a 20 a 77 a 0.0 b 20.7 a
Nova 1 4 b 125 b 19 a 99 a 0.0 b 11.5 b


Root-knot = Meloidogyne incognita, Ring = Criconemella ornata Lesion = Pratylenchus
brachyurus, Stubby-root = Paratrchodorus minor.
Root-gall index: 0 = no galling, 1 = 1 2, 2 = 3 10, 3 = 11 30, 4 = 31 -100, 5 = > 100
galls per plant.
Data in columns followed by the same letter are not significantly different according to
Duncan's new multiple range test (P = 0.05) All means are an average of 4 replications X 4
tillage treatments X 2 cropping systems X 2 sampling dates.


Table 5. Root-gall index and number of Meloidogyne incognita
juveniles in roots of vetch-corn versus vetch-grain sorghum double
cropping systems grown in a loamy sand soil of Florida.
Root-gall index No. nematodes per 10 g roots
Vetch
cultivar Vetch-corn Vetch-sorghum Vetch-corn Vetch-sorghum


Hairy 3.40 a 0.75 a 5.8 b 7.3 c
Yantage 0.20 b 0.00 a 12.8 a 7.4 c
Cahaoba 0.00 b 0.00 a 10.2 a 4.4 c
Vanguard 0.07 b 0.00 a 10.2 a 31.2 a
Nova 1 0.05 b 0.00 a 12.0 a 20.0 b

Root-gall index: 0 = no galling, 1 = 1 2, 2 = 3 10, 3 = 11 30,
4 = 31 100, 5 = > 100 galls per plant.
Means within a column followed by the same letter are not
significantly different according to Duncan's new multiple range test (P
= 0.05). All means are an average of 4 replications X 4 tillage
treatments X 2 cropping systems X 2 sampling dates.




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