#C Agronomy Research Report AY-89-06 Library
TFEB D8 199(
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Corn Yield Response to Tillage, Hybrids, and Insecticides
J.R. Espaillat and R.N. Gallaher2
ABSTRACT
Researchers have reported differential and conflicting
responses of corn (Zea mays L.) to insecticides. This research
was conducted to determine if tillage and corn genotypes could be
the reasons for these responses. Two sets of experiments were
conducted. In one 3-yr study no-tillage (NT) and conventional
tillage (CT) were main plots and four insecticide treatments were
split plots (2.2 kg a.i. Carbofuran ha-1 (CF 2.2), 1.1 kg a.i.
Carbofuran ha-1 (CF 1.1), 2.2 kg a.i. Terbufos ha-1 (TF 2.2), and
a untreated control (C). In the other set six hybrids were main
plots with the same insecticides as split plots. Grain yield and
plant height were measured at harvest. Treatments with CF 2.2
gave higher grain yield in NT, but TF 2.2 gave equal grain
response in CT. When "Asgrow RX777" (developed using TF) was
treated with TF 2.2, it averaged 32 q ha-1 more grain than the C.
Also, "DeKalb XL71" (developed using CF) yield 28 q ha- more
grain with CF 2.2 than with the C. These interactions suggested
that a hybrid will respond better to the insecticide used during
its breeding development.
Graduate student (National Corn Program, The Dominican Republic)
Professor of Agronomy, Agronomy Department, Inst. of Food and
Agr. Sci., University of Florida, Gainesville, Florida, 32611.
INTRODUCTION
Researchers have reported differential and conflicting
responses of corn (Zea mays L.) to insecticides (5).
Environmental factors influence both the magnitude and expression
of genetic resistance. Also, cultural factors such as soil
fertility, soil moisture, pesticides, and plant growth regulators
affect yield and nutritional quality of host plant tissue
appearing to be particularly important in the induction of
resistance (13). Genotypes may react differently in different
environments resulting in populations that were relatively stable
in their original environment, being unstable and fluctuating
greatly in the stress of a new environment (3, 8).
The advantages and disadvantages of no-tillage (NT) on crop
production have been reviewed by Phillips et al (11). No-tillage
induces major modifications in ecological conditions in fields,
especially the conditions affecting soil fauna. These
alterations may enhance, have no affect, or deter the
biopotential of soil arthropods including agricultural pests. It
is generally anticipated that insect infestations will be more
severe in NT systems and that insect control will be more
difficult than in conventional tillage (CT) corn (9). However,
infestations of lesser cornstalk borer (Elasmopalpus lignosellus)
were deterred in NT corn cropping systems (2). Pathogens affect
the absorption of soil applied pesticides. Both root rot
(Giberella zeae S.) and Leaf rust (Puccinia sorghi S.) affected
the translocation of carbofuran from soils into the plant (12).
The method and timing of pesticide application determine the
efficiency of application. Terbufos gave excellent season-long
control of greenbugs (Schizaphis graminum R.) and increased grain
yield when injected into soil. Equivalent rates applied in a
band on the soil surface gave poor control (4). Carbofuran
degradation in some soils is rapid, occasionally failing to
provide adequate control (6, 7). In a tillage-corn genotypes
study 60 commercial hybrids were grown under NT and CT, no
differential response of these hybrids to tillage system was
found (10).
Since high seed yield is likely the overriding objective of
the corn breeder, and since emphasis is directed to higher grain
yields for grain farmers to maintain an existence in farming,
hybrid development is likely carried out under ideal conditions
such as; fertility and pest control. These genotypes (cultivars)
would be developed under relatively specific altered
environments. Furthermore, it is proposed that a hybrid
developed for high seed yield under high fertility and ideal
irrigation may not perform well in other environments of low
fertility and/or non irrigation. The authors hypothesize that if
hybrids are developed using a specific pesticide (insecticide
and/or nematicide) it may not perform the same if grown using
another pesticide (1).
The objective of this research was to determine if tillage
and corn genotype are the reasons why scientist, industry, and
farmers disagree on yield response among pesticides.
MATERIALS AND METHODS
This research was conducted in the north-central Florida
region from 1981 to 1983. Two sets of experiments were carried
out on Hernando LFS (Typic Hapludalf) soil. In both cases, a
randomized complete block design was used. The two sets of
experiments were the following: tillage/pesticide, and
genotype/pesticide.
Tillage/Pesticide Experiments
In this 3-year study (1981, 1982, 1983) the response of
"Dekalb XL71" corn hybrid to insecticides under two tillage
management conditions was evaluated. No-tillage plus in-row
subsoil versus CT plus in-row subsoil were whole plots with four
replications and three insecticide treatments and a control were
split plots (1.1 Kg a.i. Carbofuran ha-1 (CF 1.1) 2.2 Kg a.i.
Carbofuran ha-1 (CF 2.2), 2.2 Kg a.i. Terbufos ha-1 (TF 2.2) and
a untreated control (C)). Split plots were 10 feet (3.07 m)
wide, and 30 feet (9.20 m) long. There were four rows 30 inches
(0.75 m) apart. Plots were kept under monocrop corn for 6-yr, 3-
yr prior to the implementation of the pesticide treatments, and
during the 3-yr experiment. The corn hybrid DeKalb XL71 at
90,000 seed per hectare was planted from 27 February to 10 March
each year. A Brown Harden in-row subsoil NT planter was used
either where no prior land preparation had occurred or where the
soil had been prepared conventionally with an off-set Harrow and
Rototiller. The pesticide treatments were applied in 6 inch
(0.15 m) bands over the row at planting. Complete fertilizer
including N, P, K, S, Mg, Fe, Cu, B, Zn and Mn was broadcast
prior to planting based on soil test and plant need. Preplant
broadcast fertilization include 200 Kg ammonium nitrate (NO3),
and 225 Kg KMAG ha-1. Also, Ammonium nitrate was sidedressed at
a rate of 168 Kg ha-1 when plants were 10 inches (0.25 m) tall.
Weed control was done 10 days prior to planting with Paraquat
plus X77 surfactant. When corn was about six inches (0.15 m)
tall a post-broadcast application over the top was done with
Atrazine. Atrazine at 2.2 Kg a.i. ha- and 2 L crop oil ha-1 was
used in all experiments.
Collected data consisted of plant height (PH) at the soft
dough stage of grain formation, and corn grain yield (GY) at
harvest time. Statistical analyses were performed using split
plot ANOVA on a TRS-80 model III microcomputer. Means were
tested using Duncan's new multiple range test at the 0.05
probability level.
Genotype/Pesticide Experiments
In this three-location study six commercial hybrids were
evaluated for yield as affected by pesticide treatment. This
genotype/pesticide experiment was conducted during 1982 and 1983,
having different locations. The 1982 experiment was done in
Alachua county, FL and the two 1983 experiments (1983A, 1983B)
were done in Levy county, FL. The three locations had similar
cropping histories, of continuous double cropped NT corn followed
by soybean (Glycine max L.) for 1 yr in the case of the 1982
location, and for the last 4 yr in both 1983 locations.
The hybrids evaluated were the following; Asgrow RX777(A),
DeKalb XL 71(D), Funks G4507A(F), Coker 19(C), Pioneer Brand
3320(P), and Gold Kist 748(G). Hybrids were whole plots with 4
replications. The same insecticides and rates used in the
tillage/pesticide study were split plots. The same plot size and
cultural practices used in the tillage/pesticide experiment were
used in this experiment, such as planting technique, weed
control, and fertilization rate. Data collection, and
statistical analysis were handled in the same manner.
RESULTS AND DISCUSSION
Tillage/Pesticide Experiments
The average of 3 yr of data showed interactions between
tillage and pesticide treatments for both, grain yield (GY), and
plant height (PH) (tables 1, and 2). The highest GY was given
under NT conditions by CF 2.2 which was different from the others
at the 0.05 probability level. It was followed by the other two
pesticide treatments, which did not differ in yield response to
pesticides. All pesticide treatments gave higher GY than the
Control (table 1).
Under CT conditions there was no difference (0.05 prob.
level) among pesticide treatments. However, both pesticides and
rates were better than the Control (table 1). Among the
pesticide treatments, CF 2.2 gave the highest grain yield under
NT conditions. The opposite occurred with CF 1.1, having greater
grain yield under CT conditions. But TF 2.2 did not show any
differences between tillage treatments. For the C, NT grain
yield was higher than CT.
The tallest plants also occurred under NT conditions at the
highest rate of Carbofuran (CF 2.2). The CF 1.1, TF 2.2, and C
did not differ in NT (table 2). Under CT both CF 2.2 and CF 1.1
gave the tallest plants. The TF 2.2 treatment had shorter plants
than the Carbofuran treatments. The C had the shortest plants in
CT. Among the pesticide treatments, tillage treatments were
different only for the highest rate of Carbofuran, and was in
favor of NT (figure 2).
Genotype/Pesticide Experiments
The three-location average showed interactions between
genotype and pesticide treatments under NT conditions for both GY
and PH (tables 3, and 4). Looking at the Grain Yield response to
pesticides within each individual hybrid, note that the highest
GY was obtained with Asgrow RX777 using TF 2.2 (105 g ha-1). All
the other hybrids gave their highest GY with the highest rate of
Carbofuran (CF 2.2). However, Coker 19 responded statistically
equal to Terbufos and the two Carbofuran rates. Also, Pioneer
brand 3320 responded equally to the two Carbofuran rates (table
3). For the same data, the GY response was studied across
hybrids within an individual pesticide treatment (figure 2).
This comparison showed that when CF 2.2 was used the DeKalb XL71
and Gold Kist 748 hybrids gave the highest GY. However when CF
1.1 was used Pioneer brand 3320 and Gold Kist 748 gave the
highest GY. Terbufos seemed to favor Asgrow RX777 grain yield
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over the others. When the hybrids were placed in a untreated
environment the hybrid Pioneer brand 3320 gave the greatest grain
yield.
In general the tallest plants occurred by different hybrids
with the highest rate of Carbofuran (CF 2.2). The exception was
DeKalb XL71, which had the tallest plants with TF 2.2 (246 cm).
The Control (C) gave the shortest plants. The PH response among
hybrids within an individual pesticide treatment was evaluated
(table 4). This comparison showed that for both CF rates that
were used Gold Kist 748 gave the tallest plants. The TF 2.2
favored DeKalb XL71 in PH. Again, Gold Kist 748 and DeKalb XL71
gave the tallest plants when placed in a untreated environment.
CONCLUSIONS
Tillage treatments were different for the hybrid DeKalb XL71
only when the highest CF rate (2.2 Kg a.i. ha-1) was used, being
in favor of NT. This may have been due to the Growth regulator
effects attributed to CF. The three insecticide treatments gave
equal grain yield in CT. The results showed that it is not
appropriate to use recommendations from research conducted in one
type of tillage and expect the same response in another tillage
environment. Research is needed in both NT and CT in order to
make proper recommendations to growers.
These data indicate that hybrids do not respond equally to
pesticides and this genotype/pesticide relationship is likely the
major reason why scientists disagree from one location to
another. Strong evidence was found to claim that commercial corn
breeders are selecting for a pesticide when it is used during the
development of the hybrid. This appears to be the case of Asgrow
777 which gave the highest yield when TF 2.2 was used. Terbufos
was used throughout its breeding program. All other hybrids were
developed using CF in their breeding program. In order to make
valid recommendations on pesticide use by growers, recommended
pesticides may need to be tested on all recommended hybrids in
order to match up the proper pesticide, rate of pesticide, and
hybrid for maximum response of each hybrid and maximum benefits
from the use of pesticides.
Table 1.
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Corn grain yield response to tillage and
pesticides (three year average)
Tillage
Pesticide Rate No Yes Average
kg a.i. ha-1 --------- q ha----
Carbofuran 2.2 118 a 109 a 114
Carbofuran 1.1 100 b 108 a 104
Terbufos 2.2 102 b 104 a NS 103
Control 0.0 92 c 81 b 87
Average 103 100
a,b,c, = within columns among pesticides.
* = different at .05 P in rows between tillage.
NS = nonsignificant.
Table 2. Corn plant height response to tillage and
pesticides (two year average)
tillage
Pesticide Rate No Yes Average
kg ha- ---------- cm -----
Carbofuran 2.2 266 a 252 a 259
Carbofuran 1.1 247 b 253 a NS 250
Terbufos 2.2 247 b 244 b NS 245
Control 0.0 240 b 235 c NS 237
Average 250 246
a,b,c, = within columns among pesticides.
* = different at .05 P in rows between tillage.
NS = nonsignificant.
Table 3.
Corn hybrid grain yield response to pesticides in no-
tillage management (three location average)
Insecticide Treatment
Carbofuran (CF) Terbufos (TF) Control Average
Hybrid 2.2 1.1 2.2 0.0
------------------------ q ha--------------------
A 97 v 92 w 105 u 73 vw 92
b c a d
D 103 u 92 w 90 v 75 vw 90
a b b c
C 92 w 95 vw 93 v 75 vw 89
a a a b
G 104 u 98 uv 84 w 77 v 91
a b c d
F 90 w 83 x 79 w 69 w 80
a b c d
P 98 v 101 u 89 v 91 u 77
a a b b
Average 97 94 90 77
Insecticide rates expressed as Kg a.i. ha-1. A = Asgrow RX777,
D = DeKalb XL71, C = Coker 19, G = Gold Kist G K 748, F = Funks
G4507 P = Pioneer brand 3320. a,b,c = within rows of
pesticides, values not followed by the same letter are
significantly different at the 0.05 level of probability;
u,v,w,x = within columns, values not followed by the same letter
are significantly different at the 0.05 level of probability.
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Table 4.
Corn hybrid plant height response to pesticides in no-
tillage management (three location average)
Insecticide Treatment
Carbofuran (CF) Terbufos (TF) Control Average
Hybrid 2.2 1.1 2.2 0.0
----------------------- cm----------------------
A 250 v 234 y 242 w 217 w 235
a c b d
D 242 w 237 x 246 u 236 uv 240
b c a c
C 250 v 230 z 235 x 211 x 231
a c b d
G 255 u 250 u 244 vw 237 u 247
a b c d
F 244 w 242 w 231 y 215 w 233
a a b b
P 253 u 247 v 237 x 234 v 243
a b c d
Average 249 240 239 225
Insecticides rates expressed as Kg a.i. ha-1. A = Asgrow RX777,
D = Dekalb XL71, C = Coker 19, G = Gold kist G K 748, F = Funks
G4507A, P = Pioneer 3320. a,b,c = within rows of pesticides,
values not followed by the same letter are significantly
different at the 0.05 level of probability; u,v,w,x = within
columns, values not followed by the same letter are significantly
different at the 0.05 level of probability.
140
120
100
80
60
G
R
A
I
N
Y
I
E
L
D
q
h
a
-40,
SCarbofuran 2.2 Kg/ha EM Carbofuran 1.1 Kg/ha
C Terbufoa 2.2 Kg/ha E Control (untreated)
NO-TILLAGE CONVENTIONAL
TILLAGE TREATMENT
0
Fig. 1. Corn grain yield response to tillage and pesticides
(three year average).
CF 2.2 CF 1.1 TF 2.2 0.0
PESTICIDE TREATMENT
Fig. 2. Corn hybrid grain yield response to pesticides in
no-tillage management (three location average).
40-
20
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LITERATURE CITED
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effectiveness of an insecticide. J. Econ. Entomol. 18:265-
267.
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of no-tillage corn cropping systems involving insecticides,
hybrids, and irrigation on lesser cornstalk borer
infestations. J. Econ. Entomol. 70(3):361-365.
3. Burton, G. W. 1979. Handling cross-pollinated germplasm
efficiently. Crop Sci. 19:685-690.
4. Depew L. J. and M. L. Hooker. 1987. Effect of Insecticide
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factor in Maize Silks as a means of corn Earworm
(Lepidoptera: Noctuidae) Suppression. J. Econ. Entomol.
77:487-490.
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9. Musick, G. J. 1975. Insect problems associated with no-
tillage corn production. Proc. N. E. No-tillage Conf. 1:44-
59.
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(Washington, D.C.) 208:1108-1113.
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factors influencing the magnitude and expression of
resistance, pp.87-114. in Breeding Plant Resistant to
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