Research Report 1997-98
Objective:
This study compares different methods and timing of mechanical shredding
of corn stalks of different corn maturities against no shredding and no
corn residue and their effect on no-till wheat planting for the 97-98 growing
season.
Methods:
The study was located at Princeton, Ky. on a moderately well drained
Zanesville silt loam. The previous crop was corn and the early variety
(Pioneer 3394) yielded 181 bu./ac. and the late variety (Pioneer 3167)
yielded 154 bu/ac. All crops were planted no-till (wheat and corn). Pioneer
2545 wheat was planted at 35 seeds/sq. ft. in 10 ft. X 50 ft. plots. The
soil test was pH - 6.3, P - 35, and K - 150 and 0-90-60 lb/ac. of N-P2O5-K2O
was added prior to wheat planting. Gramoxone was applied after planting
and a total of 120 lbs/ac. of N was applied with ½ on Feb. 9 and
½ on March 20. Harmony Extra was applied on March 30 and Tilt on
May 1.
Research Treatments
1. Remove all corn residue and plant into clean residue conditions
(full season corn).
2. Plant at an angle into standing harvested corn stalks (full season corn).
3. Plant directly into standing corn residue, not angled (full season corn).
4. Plant directly into standing corn residue, not angled (early season corn).
5. Rotary mow corn residue after harvest and plant into mowed residue (full season corn).
6. Flail mow corn residue after harvest and plant into mowed residue (full season corn).
7. Plant directly into standing harvested corn and flail mow after planting (full season corn).
8. Flail mow corn residue after harvest and plant into mowed residue
(early season corn).
Results:
All treatments resulted in 85-95% of residue cover after planting except
for the treatment where all residue was removed.
Wheat stands are seen in the following table. Stands were highest where all residue was removed. Flail shredding after corn harvest resulted in the next best treatment regardless of corn maturity. A step below this was rotary mowing of stalks, planting diagonally in standing corn residue and planting with the rows of the early variety of standing corn stalks. By far, the worst stands were planting with the rows of the late variety of corn and flail shredding after planting.
The two best looking treatments during the growing season was 1) all residue removed and 2) flail shredding of early maturing corn.
The yields of the treatments ranged from 54 to 62 bu/ac with almost
no statistical difference among the treatments. The yields were low due
to the freeze and high May temperatures and were not high enough to allow
separation of the better treatments. In fact, some of the better treatments
in terms of stands and early growth were not among the highest yielding.
| Effect of Residue Management on Wheat Stand in November | ||
| Treatment | Corn Maturity | Wheat Stand (Plants/sq ft) |
| 1. Removed all corn residue | Full | 26.8 a |
| 2. Residue behind combine (as is)
diagonally planted |
Full | 21.4 cd |
| 3. Residue behind combine (as is) | Full | 16.7 e |
| 4. Residue behind combine (as is) | Early | 20.0 d |
| 5. Rotary mowed after harvest | Full | 21.2 cd |
| 6. Flailed after harvest | Full | 24.3 b |
| 7. Flailed after wheat planting | Full | 17.9 e |
| 8. Flailed after harvest | Early | 22.4 c |
Double-Cropped Soybean Stands
Double-cropped soybeans were planted after wheat harvest and the best
stands were achieved where wheat had been planted diagonally behind standing
corn residue.
Conclusions:
This is only the first year of this experiment, so results may change
with time. Stands were best when all residue was removed, but flail shredding
of corn after harvest gave similar results and appeared to be an excellent
alternative. Flail shredding was better than rotary mowing or planting
into standing corn residue. The worst treatment in all respects was flail
shredding after wheat planting.
No-Tillage
Wheat
Lloyd Murdock, Jim Herbek, Jim Martin, John James and Dottie Call
University of Kentucky
Objective:
The objective of this experiment is to see if high yields can be produced
by no-till wheat and to see if no-till wheat is an economical alternative
to conventionally planted wheat on a long term basis. The experiment includes
different tillage methods, nitrogen rates and herbicides.
Methods:
The experiment is at Princeton, Ky on a Pembroke silt loam soil that
is moderately well drained. Pioneer 2540 was planted on Oct. 10 at 35 seeds/sq.
ft. Conventional plots were chisel plowed and disked twice. The plots were
10 ft. x 30 ft. The soil test was pH-6.3, P-39, and K-169 and 0-60-50 lb/ac.
as N-P2O5-K2O was applied before planting.
Gaucho insecticide was coated on all seed at 2 oz/100 wt. and Tilt was
sprayed at 4 oz/ac. at heading.
Results:
The method of planting (no-till vs. conventional) had a significant
effect on yields this year and the conventional tillage treatment yielded
7 bu/ac. more than no-till wheat. The reduction in yield by no-tillage
may have been due to the freeze in March and more vole damage. The six-year
average is about 5.5 bu/acre greater for the conventional tillage treatment.
| Yields According to Tillage | ||
| Treatment | 1998 Yields
(bu/ac) |
Yields
('93-'98) |
| Conventional | 85 a | 93.3 |
| No-Till | 78 b | 87.8 |
Nitrogen was managed for intensive production with 1/3 of N applied
at Feekes 3 and the remainder at Feekes 5. Increasing the N rate from 90
to 120 lb/ac. had little effect on yield this year. There is also little
difference in the six-year average yields.
| Yields According to Nitrogen Rate | ||
| Treatment
(lb/ac) |
Yields
(bu/ac) |
Yields
('93-'98) |
| No-Till 90 | 76 b | 86.0 |
| No-Till 120 | 79 b | 87.8 |
| Conv. 90 | 86 a | 91.5 |
| Conv. 120 | 83 a | 93.8 |
Weeds were mainly common chickweed, henbit, and a small amount of cheat.
In general, the level of weed control for conventional till plots treated
with Harmony Extra in the spring were equal to the no-till plots treated
with Gramoxone Extra in the fall followed by Harmony Extra in the spring.
Treatment of no-till with only Harmony Extra in the fall or spring resulted
in weed control sufficient for high yields. Cheat was found in only small
amounts in the no-till plots. The weed pressure in the untreated no-till
plots did not reduce the wheat yields this year but the six-year average
yields show that weed control is important. The six-year average indicates
that all 3 of the no-till weed control treatments used are about equally
effective for yield.
| Herbicide Treatments | ||
| Treatment | 1998 Yields
(bu/ac) |
Yields
('93-'98) |
| No-Till - Fall Harmony Only | 77 a | 89.2 |
| No-Till - Spring Harmony Only | 75 a | 87.8 |
| No-Till - No Herbicides | 75 a | 75.3 |
| No-Till - Peak | 77 a | |
| No-Till -Fall Gramoxone
Spring Harmony |
79 a | 89.8 |
The fall stand counts over a five-year average show about 10% less plants
in the no-till plots as compared to the conventional plots when planted
at the same rate. This year plant counts were almost identical for the
two treatments.
| Wheat Stands (Plants/sq. ft.) | ||
| Treatment | Fall - 1998 | Fall (5 Yrs. Avg.) |
| No-Till | 26.6 | 25.6 |
| Conventional | 26.5 | 27.6 |
Conclusions:
High yields can be obtained with no-till wheat. Yields are about 6%
less than with till planted wheat. In many years, the yields were the same.
The years when the no-till yields were lower are primarily associated with
winter or spring freezes. Chemical weed control is important, but can be
achieved by several methods.
Objective:
The objective of this experiment was to verify the effects of no-till
wheat and tilled wheat on the subsequent yield of soybeans and corn planted
after wheat and measure differences in fertility and physical effects on
the soil on a long term basis.
Methods:
The experiment is at Princeton, Ky on a Pembroke silt loam soil that
is moderately well drained. Pioneer 2540 was planted on Oct. 10 at 35 seeds/sq.
ft. Wheat was planted no-tilled and with tillage and the tillage plots
were chisel plowed and disked twice. The plots were 10 ft x 30 ft. The
soil test was pH - 6.3, P - 39, and K-169 and 0-60-50 lbs/ac of N-P2O5-K2O
was applied before planting. N was applied on wheat at 90 lbs/ac. on ½
of the plots on at 120 lb/ac. on the other half. Gaucho insecticide was
coated on all seed at 2 oz/100 wt. and Tilt was sprayed at 4 oz/ac. at
heading.
Results:
Yields of Succeeding Crops
Both soybeans and corn are no-tilled after the two tillage systems
in which wheat is grown. The soybeans are double-cropped after the wheat
and the corn is planted the next spring before the wheat is planted in
the fall. These crops are harvested for yield to determine if the wheat
tillage systems had an effect.
The data (below) indicates that both corn and soybeans tend to yield more (about 5%) where the wheat is planted no-till. However, the differences are not always statistically significant, but the trend has remained consistent since the second year of the experiment.
The data indicates that some changes in the system which have taken place in the two systems is more favorable for these crops when planted after no-till wheat. The reason for the difference is not clear at this time, but might include residue cover, soil moisture, soil physical changes, or others.
Soil Changes
The soil density and the soil strength have been measured each year
and both of these measures show very similar readings with no differences
between the two systems indicating that compaction is not a problem in
either system.
The amount of soil organic matter found in the two systems was very similar. One would expect the all no-tillage treatment to have more organic matter, but there is no statistical difference. There is also no difference in the soil test pH, phosphorus or potassium between the two systems.
Temperature and Wheat Growth
Temperature loggers were placed at different heights and depths within
the soil and wheat canopy to develop a temperature profile that might help
answer questions concerning the differences between tilled and no-tilled
wheat on growth vigor and winterkill.
Late winter freeze damage occurred in March of 1998. The data collected
indicates that no-tillage conditions may lower the temperatures compared
to the tilled wheat. The coldest temperature occurred on March 12 and the
temperature at ground level was as low as 13o F in the conventional
stand and 7o for the no-till stand. However, the wheat was at
Feekes 5, so we did not observe any differences in winter damage. The no-till
plants turned yellow and were a little slow to recover, but the number
of heads were unaffected.
| Effect of Wheat Tillage Systems on the Yield of Succeeding Crops | ||
| Year | Wheat Tillage System | |
| No-Till | Conventional | |
| Soybeans (bu/ac) | ||
| 1998 | 16.5 | 15.8 N.S.* |
| 1997 | 45.1 | 42.7 N.S. |
| 1996 | 54.5 | 50.8 N.S. |
| 1995 | 24.4 | 22.2 N.S. |
| 1994 | 49.5 | 51.6 N.S. |
| Avg. | 38.0 | 36.6 |
| Corn (bu/ac) | ||
| 1998 | 203.7 | 190.2** |
| 1997 | 211.9 | 199.3 N.S. |
| 1996 | --- Harvest Data Lost --- | |
| 1995 | 186 | 191 N.S. |
| 1994 | 206 | 178 ** |
| Avg. | 201.9 | 189.6 |
| * N.S. means no significantly statistical
differences.
** Statistically different at the 0.1% level. |
||
Conclusions:
No-tillage wheat seems to have a favorable effect on the yields of
the subsequent crops (corn and soybeans) planted in the rotation. Yields
of these two crops are increased about 5 to 6% on the average when planted
after no-till wheat. The reason of this is unclear at this time. The temperature
extremes are greater under the no-tillage wheat planting which can increase
the changes of freeze damage.
Introduction:
Italian ryegrass (Lolium multiflorum) is increasing as a problem
weed in wheat. It is a cool-season annual that emerges in the fall and
matures around late June to early July. Italian ryegrass plants may mature
near wheat harvest time; therefore, its seed can spread behind the combine
during the harvesting process.
The similarity in the life cycles of Italian ryegrass and wheat may provide an opportunity to use a preharvest treatment of Roundup Ultra (glyphosate) to limit the viability of Italian ryegrass seed and spread of this problem weed. The Roundup Ultra label recommends that applications be made after wheat has reached the hard-dough stage of grain (30% or less grain moisture). In order for this treatment to be successful, applications must be made before ryegrass has matured and wheat seed reaches the hard-dough stage.
Objective:
Evaluate the impact of preharvest application of Roundup Ultra on control
and seed viability of annual ryegrass.
Methods:
Madison wheat was seeded October 22, 1997 at a rate of 35 seed/ft2
at the UKREC in Princeton, Kentucky. The plot area had a 3-year history
of annual ryegrass. Nitrogen in the form of ammonia nitrate was applied
as a split treatment of 60 units (2-24-98) plus 60 units (3-24-98).
Preharvest treatments of Roundup Ultra at 2 pt/A were applied at two times:
Preharvest I = June 2 and an average wheat grain moisture of 49.3 %
Preharvest II = June 11 and an average wheat grain moisture of 26.1
%
The following data were collected:
1. Annual ryegrass control ratings: Visual ratings were made on June 23 and were based on a 0 to 100 scale with 0 = no control and plants were green in color and 100 = plants dead with no green color.
2. Annual ryegrass and wheat seed germination: Seedheads were collected at random from each plot. Seeds were threshed by hand and analyzed by University of Kentucky Regulatory Services for percent germination.
Results:
Timing had a significant impact on effectiveness of the Roundup Ultra
preharvest treatments. The preharvest I treatment provided 100 % control
of annual ryegrass compared with 47% control with the preharvest II treatment
(Table 1). The annual ryegrass seed from the preharvest I treatment had
only 38% germination compared with 88% for preharvest II treatment and
93% for the nontreated check. The wheat seed collected from the preharvest
I treatment had 82% germination which was significantly less than the 93%
germination for the wheat seed from the nontreated check. The viability
of the wheat seed from the preharvest II treatment tended to be slightly
less in comparison with the nontreated check, however, this difference
was not statistically significant.
_
| Table 1. Impact of Timing of Preharvest Applications of Roundup Ultra at 2 pt/A on Annual Ryegrass and Wheat. | ||||
| Timing1 |
|
|
||
| Roundup Ultra 2 pt/A | Preharvest I |
|
|
|
| Roundup Ultra 2 pt/A | Preharvest II |
|
|
|
| Nontreated Check |
|
|
|
|
| LSD (0.05) |
|
|
|
|
| Timing1: Preharvest I applied
on 6-02-98 (49.3% wheat seed moisture).
Preharvest II applied on 6-11-98 (26.1% wheat seed moisture). |
||||
Conclusions:
These results indicate Roundup Ultra provided effective control of
annual ryegrass plants and significantly reduced annual ryegrass seed viability
when the herbicide was applied earlier than the hard-dough stage (i.e.
30% moisture) label restriction. The nine days that lapsed between the
preharvest I and II treatments appeared to allow time for annual ryegrass
seed to become mature and maintain its viability. It is important to note
this research is based on only one season and may not represent all situations
when using preharvest treatments of Roundup Ultra. Additional research
is needed to determine if differences in the maturity of wheat and annual
ryegrass seed are large enough to allow safe and legal use of Roundup Ultra
as a preharvest application in wheat.
Managing
Weedy Grasses with Fall and Spring
Applications of Hoelon
James R. Martin, Extension Weed Scientist
Justin Ewing, Graduate Student
William Witt, Professor
Introduction:
Cool-season weedy grasses are increasing in occurrence as problem weeds
in wheat in Kentucky and surrounding states. Examples of weedy grasses
that can be found in wheat included Italian ryegrass (Lolium multiflorum),
cheat (Bromus secalinus), downy brome (Bromus tectorum),
field brome (Bromus arvensis), and hairy chess (Bromus commutatus).
These species often emerge in the fall and develop most of their growth
the following spring.
Italian ryegrass can be controlled with Hoelon depending on size of plants. The Hoelon label recommends using the 1.33 pt/A for controlling 1- to 4- leaf plants, 2 pt/A for 5-leaf plants, and 2.67 for 5-leaf to 2-tiller plants. When compared with Italian ryegrass, the Brome species tend to be more tolerant to Hoelon and are not listed on the label for Kentucky.
Objective:
Evaluate control of annual ryegrass and hairy chess and wheat yield
following fall and spring applications of Hoelon .
Methods:
The plot area was chisel plowed and disced prior to planting. Madison
wheat was seeded at a rate of 35 seed/ft2 October 22, 1997 at
the UKREC in Princeton, Kentucky. The plot area had a history of a mixed
population of annual ryegrass and hairy chess. Nitrogen in the form of
ammonia nitrate was applied as a split treatment of 60 units (2-24-98)
plus 60 units (3-24-98).
Hoelon 3EC (diclofop-methyl) was applied at the rate of 2 pt/A in a
spray volume of 26 GPA. The timing of application and size of wheat and
weedy grasses are indicated below:
Date Wheat Weedy Grasses
Fall treatment: 12-20-97 1 tiller 2" tall 1-1.5" tall
Spring treatment
4- 6-98
3 tiller 8" tall
5" tall
Visual ratings of biomass for wheat, annual ryegrass, and hairy chess
were made May 30, 1998. Plots were harvested for grain yield July 7, 1998.
Results:
The biomass ratings in May indicated that Italian ryegrass accounted
for 89% of the plant biomass in the plots relative to only 1% for hairy
chess (Table 1). The competition from these weedy grasses, particularly
Italian ryegrass, limited the wheat yield in the check plots to only 3.8
bu/A.
The results from the herbicide treatments confirmed that Hoelon is more
effective in managing Italian ryegrass than hairy chess. Both fall and
spring treatments improved control of Italian ryegrass and allowed hairy
chess to develop and become the more dominant of the two species. The fall
treatment was generally more effective than the spring treatment in limiting
the amount of growth of both species; consequently, the 26.2 bu/A wheat
yield achieved with the fall treatment was significantly greater than the
yield from the spring treatment or the nontreated check. In spite of the
improved control with the fall treatment, the hairy chess still accounted
for nearly one-third of the plant biomass and seemed to restrict wheat
yield.
| Table 1. Impact of Fall and Spring Applications of Hoelon at 2 pt/A on Biomass of Wheat, Annual Ryegrass, and Hairy Chess and Wheat Grain Yield. | |||||
| Timing1 |
Plant Biomass2
Annual Hairy Wheat Ryegrass Chess ------------- % ---------- |
(Bu/A) |
|||
| Hoelon 2 pt/A | Fall |
|
|
|
|
| Hoelon 2 pt/A | Spring |
|
|
|
|
| Nontreated Check |
|
|
|
|
|
| LSD (0.05) |
|
|
|
|
|
| Timing1: Fall treatment was applied
on 12-20-97. Spring treatment was applied on 4-6-98.
Plant Biomass2 : Percentages represent the relative amount of plot area occupied by wheat, annual ryegrass, and hairy chess based on visual ratings made on 5-30-98 . |
|||||
Conclusions:
Applying Hoelon to a mixed population of Italian ryegrass and Brome
species, such as hairy chess, may result in effective control of the Italian
ryegrass and allow the Brome species to emerge as the dominant species.
The use of Hoelon in the fall when plants are small will likely result
in better control of Italian ryegrass than waiting until the spring when
plants have overwintered and increased in size. Although hairy chess is
considered tolerant to Hoelon, there appeared to be better control of this
species where Hoelon was applied in the fall rather than in the spring.
It is unclear whether this benefit was attributed to suppression from Hoelon
or possibly the hairy chess in the fall-treated plots was further along
in its development and was more prone to the unusual freezing temperatures
that occurred in March.
Objective:
An experiment was established on the Walnut Grove Farm in Logan County,
Kentucky to determine the effects of various foliar fungicide treatments
on fusarium head blight (FHB) and various other foliar and head diseases
in a commercial field.
Methods:
The sort red winter wheat variety 'Clark' was planted into triple-disced
corn stubble in a field with a history of high crop productivity, but also
with a history of significant FHB. The field has followed a corn - wheat/soybean
rotation for many years. A significant level of corn residue existed in
the field despite the tillage operations. Plots six rows wide, 7-in. between
rows, and 10 ft-long were planted on October 14, 1997 at a density of 35
seed/ square-ft. Nitrogen was applied in the spring as a split application:
30 lbs of actual N/A (ammonium nitrate 34-0-0) were applied on February
19, 1998 and 60 lbs were applied on March 15, 1998. Fungicidal treatments
were applied to plots in the very early flowering stages (Feeke's stage
10.51) using a CO2 pressurized backpack sprayer with boom equipped with
TeeJet flat fan (80067) nozzles delivering 20 gal/A at 40 psi. Treatments
were replicated six times and were arranged following a randomized complete
block design. Plots were rated for FHB incidence and severity and Stagonospora
nodorum leaf and glume blotch at the early dough stage on May 21, 1998.
Plots were harvested on June 11, 1998 using a Hege small plot combine.
Harvested grain was dried to 12% moisture and seed yield and test weights
were determined. Percent standard germ, percent Fusarium infection,
and vomitoxin levels were determined for a subset grain sample from each
test plot after harvest.
Results:
Levels of FHB were extremely low in the test. As a result, neither
FHB incidence nor severity were significantly different among treatments.
Similarly, vomitoxin levels in all plots were extremely low (none above
0.4 ppm and most 0.3 ppm or less; data not shown). Unlike FHB scab, Stagonospora
nodorum leaf and glume blotch were severe in the test late in the season,
but levels of the diseases were low at the time fungicide treatments were
applied. All treatments except Benlate 50DF (0.5 lb/A) + Dithane 75 DF
(1.0 lb/A) + CS-7 (0.12% v/v) resulted in significantly lower leaf blotch
compared to non-treated plots. In contrast, only Quadris 2.08 SC (0.2 lb
a.i./A) + crop oil (1% v/v) significantly reduced the incidence of glume
blotch in plots. All fungicidal treatments reduced the severity of glume
blotch, albeit at different efficiencies. Quadris treatments, in particular,
appeared to have the most activity in reducing glume blotch severity. Yields
and test weights were generally below standard because of unseasonably
high temperatures during early to mid grain fill. All treatments except
Benlate + Dithane + CS-7 significantly increased yields compared to non-treated
plots. In contrast, only the Quadris + Benlate treatment significantly
increased test weight compared with the control. Standard germination and
percent Fusarium infection were similar among treatments.
|
|
|
|
|
|
|
|
|
|
|
2. Tilt 3.6E 4.0 fl oz 5.7 b 100 b 9.6 c 2.0 0.8 45.7 ab 48.8 b 90.0 12.7
3. Folicur 3.6F 4.0
gl oz
X77 0.25% v/v 4.8
a
90.0 b
6.6 bc
5.0
0.8
46.7 ab
49.3 ab
89.5
15.7
4. Quadris 2.08 SC
0.2 lb a.i.
+ Crop
oil 1% v/v 4.8 a
76.7 a
2.8 a
13.3
1.4
47.4 a
48.8 b
86.2
21.3
5. Quadris 2.08 SC
0.2 lb a.i.
+ Benlate 50 DF 0.5 lb
+ Crop oil 1% v/v 5.5 b
95.0 a
3.9 ab
7.0
2.4
49.7 a
51.2 a
89.2
18.0
6. Benlate 50
DF 0.5 lb
+ Dithane 75 DF 1.0 lb.
+ CS-7 0.12% v/v 7.5 c
100 b
17.1 d
11.7
2.0
42.5 bc
48.3 b
90.7
18.0
Conclusion:
FHB levels were too low in the test to see any potential benefit from
the fungicide treatments. However, an early flowering application of most
fungicide treatments did an excellent job of controlling Stagonospora leaf
and glume blotch, which was at moderate levels in the test. It is clear
from the data that grain yield can be significantly increased by the proper
timing of fungicides, even in a low-yielding environment, when disease
pressure is moderate and is at low levels when the crop begins to flower.
Principle Investigators: Phillip Needham and Richard Bayless, Miles
OptiCrop
Chris Bowley and Scott Jones, Wheat Tech
Objective:
To survey wheat fields to determine the link of various production
practices/situations on the incidence and severity of Fusarium Head Blight
(FHB).
Methods:
One-hundred wheat fields were identified in the fall of 1997 for inclusion
in the FHB survey. Fields surveyed were those already under contract with
either OptiCrop or Wheat Tech; each group was responsible for selecting
and scouting 50 fields. The data sheet used in the survey was based on
input from a biostatistican. Data collected in the fall included: field
identity, county, previous crop, planting date, variety, and percent residue
cover. In the spring, one-hundred heads, 25 in four locations, were collected
from each field after crop flowering and each head was rated for FHB severity
according to a picture sheet developed at North Dakota State University.
Other data taken in the spring were estimates of yield potential and peak
flowering date. Data for 99 fields (one field was lost due to the early
1998 spring freeze) were analyzed using appropriate statistical procedures.
Results:
Ninety-nine fields in four states and 18 counties were surveyed (Table
1). Four Wheat Tech scouts and one OptiCrop scout generated the survey
data. Most of the data were collected during regularly scheduled field
visits, but one additional visit to each field was made in order to make
FHB assessments. FHB was most severe in the southern tier counties of Kentucky
and Robertson County, TN compared with the other counties surveyed. Table
2 summarizes the results of statistical tests. FHB incidence and FHB severity
were highly correlated. Significant relationships were detected between
FHB incidence and corn residue, yield potential, planting date and peak
flowering date. However, the variability of these associations was such
that none of the relationships were very strong. Yield potential and corn
residue had only a modest correlation with incidence (R-squared 0.35 and
0.28, respectively). Planting date and flowering date had extremely poor
relationships with FHB incidence. All in all, the above variables could
only explain about 75% of the variation in FHB incidence ratings. In other
words, other factors beside yield potential, corn residue cover, planting
date, and peak flowering date are at play in determining FHB levels. Weather
effects, which were not accounted for by the survey, probably played the
greatest role in determining FHB.
Table 1. States and Counties Involved in the FHB,
1997-98
State County No. Field
KY
Caldwell
2
Christian
4
Daviess
5
Hardin
9
Henderson
3
Hopkins
1
Larue
1
Logan
15
McLean
8
Simpson
15
Todd
9
Trigg
1
Warren
8
Webster
2
TN
Robertson
7
IL
Lawrence
1
IN
Gibson
5
Spencer
3
Total
99
Table 2. Summary of Relationships with FHB Incidence
Parameter P Value # R-Square**
Severity N/A
(non-linear model)
.93
Yield Potential
<0.0001
.35
Corn Residue (99*) <0.0001
.28
Corn Residue (81*) <0.0001
.21
Planting Date
0.02
.06
Flowering Date
0.04
.04
Research Objective:
Verify the proper spring nitrogen rate for no-till wheat and determine
if a specific ratio of the nitrogen split between late winter N and spring
N is better. A secondary objective looked at the need for additional N
after a severe spring freeze.
Method:
Location
Logan County
Soil type and & drainage
Pembroke silt loam (well drained)
Previous Crop
Corn, Wheat, Soybeans rotation
Tillage
No-Till
Planting Date
Oct. 8, 1997
Variety
Pioneer 2540
Soil Test (lb/ac)
pH-6.3, P-52, K-312, Mg-120, Ca-3050
Type
Rate of Application
Date of Application
Fertilizer
18-46-60
100 lb/ac
09/25/97
Fertilizer
Nitrogen
(see Table 1)
02/24/98 (Feekes 3)
Fertilizer
Nitrogen
(see Table 1)
03/24/98 (Feekes 6)
Fungicide
Tilt
4 oz/ac
05/05/98 (Heading)
Insecticide Warrior
3 oz/ac
11/25/97
Insecticide Warrior
3 oz/ac
05/05/98
Herbicides Harmony
Extra
0.5 oz/ac
11/25/97
Results:
Table 1. Effect
of N on Yield
N Treatment
Yield (13.5% H2O)
February March
Total
--------------- lb/ac ---------------
----- bu/ac -----
30
90
120
75.4a
50
50
100
74.9 ab
40
40
80
74.2 ab
30
70
100
72.9 abc
60
60
120
69.8 bc
30
110
140
68.5 c
0
120
120
68.3 c
0
0
0
47.0 d
Conclusion:
The yields were good but not exceptional.
High rates of N were not needed to obtain the maximum yields. The 80 lb/ac
rate resulted in yields as high as the 120 lb/ac rate. The yields of treatments
with the same total rate of N but with different ratios applied between
Feb. and March were about the same in most cases. The treatments with the
high rates of N added in March, after the freeze, was not helpful and actually
resulted in the lowest yields. This is contrary to what might have been
expected. In May, these two treatments were visually better than the other
treatments. This indicates that looks are many times not important, we
just think they are!
Research Objective:
Determine the economic contribution of
wheat to the long-term productivity of the 3 crops/2 years rotation.
Method:
Location
Fayette County/Spindletop
Soil Type and Drainage
Maury silt loam - well drained
Previous Crop
Corn
Tillage
No-Tillage (Lilliston 9680)
Cultivar
Pioneer 2552
Planting Date/Rate
Oct. 23, 1997; 28 seed/sq. ft
Harvest Date
June 26, 1998
Fertilizer:
Nitrogen - 40 lb N/ac as 34-0-0 on 11/4/97
40 lb N/ac as 34-0-0 on 3/15/98
80 lb N/ac as 34-0-0 on 4/13/98
Herbicide:
Harmony - 0.6 oz/ac on 3/19/98
Fungicides:
Bayleton 50WP - 4 oz/ac on 4/24/98
Tilt 3.2EC - 4 fl oz/ac on 5/11/98
Results:
Average of 4 replications - 62.4 bu/acre
Conclusions:
Yields were good, but not great. Historically,
the yield of no-tillage wheat in these plots has been negatively related
to the yield of the previous corn crop . Average yield losses appear to
be about 1 bu/ac of wheat for every 10 bu/ac in the preceding corn crop,
with corn yields ranging between 90 and 190 bu/ac. The extremely low wheat
yield observed in 1990 was excluded from the relationship. This relationship
exists probably because greater corn yields are associated with greater
corn residue levels, which hinder wheat stand establishment and may also
reduce/delay wheat tillering.
Research Objective:
Determine whether redistribution of corn
residues, relative to the planted wheat row, will improve wheat yields.
Method:
Location
Fayette County/Spindletop
Soil Type and Drainage
Maury silt loam - well drained
Previous Crop
Corn
Tillage
No-Tillage (Lilliston 9680)
Cultivar
Pioneer 2552
Planting Date/Rate
Oct. 23, 1997; 28 seed/sq. ft
Harvest Date
June 26, 1998
Fertilizer:
Nitrogen - 40 lb N/ac as 34-0-0 on 11/4/97
40 lb N/ac as 34-0-0 on 3/15/98
80 lb N/ac as 34-0-0 on 4/13/98
Herbicide:
Harmony - 0.6 oz/ac on 3/19/98
Fungicides:
Bayleton 50WP - 4 oz/ac on 4/24/98
Tilt 3.2EC - 4 fl oz/ac on 5/11/98
Results:
Average of 4 reps.
| Residue Placement
Treatment |
Wheat Yield
(bu/ac) |
| random coverage | 73.8 b |
| moved 0.25 inches away | 75.4 b |
| moved 0.50 inches away | 73.1 b |
| moved 0.75 inches away | 75.0 b |
| moved 1.25 inches away | 72.0 b |
| bare (no residue) | 81.9 a |
Conclusions:
We removed corn residues prior to seeding
the wheat, then returned residues, at a rate of 6300 lb/ac (equal to about
150 bu/ac corn crop), in specific "placements" to each plot. We removed
residues prior to seeding to take out any effect of residue on the drill's
ability to establish the crop. In our "placement" treatments, we had one
where the full rate of residue was randomly scattered over the entire plot
area, four treatments where the residue was placed a set distance (0.25,
0.50, 0.75, and 1.25 inches) away from either side of the row, and a control
treatment (bare) where none of the residue was returned. The row spacing
was 7 inches.
Yields were not influenced by residue placement
treatments; only complete residue removal had a positive effect on yield
(Table 1). Measurements of soil and air temperatures during the fall emergence
and tillering period showed that residues tended to "buffer" against quick
temperature changes. This keeps the soil warmer during cooling trends,
and cooler during warming trends, and causes greater differences in temperature
between the soil and air at such times. This greater "shear" between air
and root zone temperatures might be contributing to stress during shoot
development.
Research Objective:
Determine whether the soil management
system (no-tillage vs. chisel plowing) will influence the fertilizer nitrogen
requirement of wheat following full-season soybean.
Method:
Location
Fayette County/Spindletop
Soil Type and Drainage
Maury silt loam - well drained
Previous Crop
Soybean
Tillage
No-Tillage (Lilliston 9680)
Chisel Plow + Secondary Discing
Cultivar
Foster
Planting Date/Rate
Oct. 23, 1997; 29 seed/sq. ft
Harvest Date
June 27, 1998
Fertilizer:
Nitrogen - 20% of all N rates as 34-0-0 on 11/28/97
20% of all N rates as 34-0-0 on 3/15/98
60% of all N rates as 34-0-0 on 4/13/98
Herbicide:
Harmony - 0.6 oz/ac on 3/19/98
Fungicides:
Bayleton 50WP - 4 oz/ac on 4/24/98
Tilt 3.2EC - 4 fl oz/ac on 5/11/98
Results:
Average of 4 reps.
| Fertilizer N (lb/ac) | Yield (bu/ac) |
| Fall | Spring | Total | Chisel | No-Till |
| 0 | 0 | 0 | 39.9 c | 38.3 c |
| 10 | 40 | 50 | 63.2 b | 61.6 b |
| 20 | 80 | 100 | 71.1 a | 70.6 a |
| 30 | 120 | 150 | 70.5 a | 75.6 a |
Conclusions:
In this, the first year of this experiment,
wheat following chisel plowed soybean residues averaged 61.2 bu/ac, while
no-till wheat was not significantly different, averaging 61.5 bu/ac. There
was a good response (+31.8 bu/ac) to fertilizer nitrogen, with yields increasing
with greater fertilizer N rate, up to a total N rate of 100 lb N/ac (80
lb N/ac in the spring). Interestingly, tillage had no influence on the
observed pattern in wheat yield response to fertilizer N.
Research Objective:
Determine whether the optimal N fertilizer
rate will differ among several N sources for late planted no-till wheat
following corn or full-season soybean.
Method:
Location Fayette
County/Spindletop
Soil Type and Drainage
Loradale silt loam - well drained
Previous Crops
Soybean Corn
Tillage
No-Tillage (Lilliston 9680)
Cultivar
Pioneer 2540
Planting Date/Rate
Nov. 23, 1997; 20 seed/sq. ft
Harvest Date
July 1, 1998
Fertilizer:
Four Nitrogen Sources - slow release urea (40-0-0) provided by Chisso Corp.
100% of all N rates on 11/28/97
- urea (46-0-0);
- ammonium nitrate (34-0-0);
- urea-ammonium nitrate solution (28-0-0):
25% of all N rates on 11/28/97
25% of all N rates on 4/2/98
50% of all N rates on 4/23/98
Herbicide:
Harmony - 0.6 oz/ac on 3/19/98
Fungicides:
Not Needed
Results:
Average of 4 reps. - See Table 1, below.
Conclusions:
Yield of this late-planted no-till wheat
was positively influenced by fertilizer N addition and soybean, as opposed
to corn, as a previous crop (Table 1). Wheat following soybean averaged
nearly 15 bu/ac greater yield than wheat following corn in this study.
Averaged across all N rates, and regardless of prior crop, no difference
due to fertilizer N source was observed. The optimal N rate was between
a total of 105 and 140 lb N/ac, regardless of N source and previous crop.
The slow-release urea was equal in performance to the other sources, despite
being applied entirely in the fall.
|
|
N Applied |
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Research Objective:
Determine whether no-tillage wheat following
corn requires an earlier planting date and greater attention to early N
applications (both fall and early spring) than wheat planted in a tilled
seedbed.
Method:
Location
Fayette County/Spindletop
Soil Type and Drainage Donerail silt
loam - moderately well drained
Previous Crop
Corn
Tillage
No-Tillage (Lilliston 9680) - Chisel Plow + Secondary Discing
Cultivar
Pioneer 2568
Planting Dates
Oct. 16, 1997; Oct. 30, 1997; Nov. 25, 1997
Seeding Rate
41 seed/sq. ft
Harvest Date
July 3, 1998
Fertilizer:
Nitrogen - Fall - 0& 40 lb N/acre as ammonium nitrate (34-0-0) on 11/28/97
Early Spring - 0& 40 lb N/acre as ammonium nitrate (34-0-0) on 3/16/98
Late Spring - 80& 120 lb N/acre as ammonium nitrate (34-0-0) on 4/20/98
Herbicide:
Harmony - 0.6 oz/ac on 3/19/98
Fungicides:
Bayleton 50WP - 4 oz/ac on 4/24/98 Tilt 3.2EC - 4 fl oz/ac on 5/11/98
Results:
Average of 4 reps. - See Table 1, below.
Conclusions:
Stand establishment was excellent
at all planting dates in this experiment (Table 1). The last planting date
gave the greatest plant density at harvest time, but the fewest number
of heads per plant. Kernels per head were greater at the later two planting
dates, and as kernel size was generally not affected by late planting,
yields were similar across all planting dates (ave. 78 bu/ac). This was
unexpected, but a cool spring contributed to improved grainfilling in the
later planted wheat. Chisel plow tillage generally improved yields (+5
bu/ac), but this response was not explained by any of the yield components
(Table 1). There was no interaction between planting date and tillage,
i.e. no-till wheat was not more inferior with later planting.
Fall application of nitrogen slightly improved yield (+3 bu/ac), but again the response was not explained by any of the yield components (Table 1). Early spring N applications resulted in a large yield increase (+11 bu/ac), which was associated with slightly greater final plant stands, greater kernel numbers per head and a modest reduction in kernel size. Late spring N did not raise wheat yield, probably because the modest increase in kernels per head was offset by the decline in kernel size.
Table 1. Effect of Planting Date, Tillage and N Timing
on Wheat Stands, Development and Grain Yields
|
|
|
|
|
|
Stand |
/Plant |
/Plant |
Size |
Yield |
Main Effect of Planting Date
1
359 b
2.4 a
21 b
29 a
77 a
2
393 b
2.2 b
24 a
27 a
79 a
3
508 a
1.6 c
24 a
28 a
79 a
Main Effect of Tillage System
NT
421 a
2.1 a
22 a
27 a
76 b
Ch
419 a
2.0 a
24 a
29 a
81 a
Main Effect of Fall N Rate
0
419 a
2.1 a
23 a
28 a
77 b
40
421 a
2.1 a
23 a
28 a
80 a
Main Effect of Early Spring N Rate
0
407 b
2.1 a
21 b
29 a
73 b
40
433 a
2.0 a
25 a
27 b
84 a
Main Effect of Late Spring N Rate
80
412 a
2.1 a
22 b
29 a
78 a
120
428 a
2.1 a
24 a
27 b
79 a
Research Objective:
To determine if carefully managed no-till
wheat can be as profitable for Ky growers as carefully managed conventional
till wheat.
Method:
Each of the three research groups chose
a field site, two wheat varieties, and independently managed their own
test. Each test included two replications of no-till versus conventional
tillage, and each tillage system included two wheat varieties. The preceding
crop was corn for all three tests. Plot sizes were a minimum of 3000 square
feet.
UK Test Information:
Location:
Spindletop Farm, Lexington, KY
Soil type and & drainage:
Maury silt loam, well-drained
Conventional tillage:
chisel plowed, then disked twice
Planting Date:
October 16, 1997
Varieties:
Foster and Pioneer 2540
Fertilizer:
85 #/A on P2540 CT; 90#/A on Foster CT; 105 #/A on P2540 NT;
and 110#/A on Foster NT. (applied as ammonium nitrate on April 1, 1998).
Fungicide:
4 oz/A on Foster only on May 12, 1998
Herbicide:
0.6 oz/A on November 12, 1997
Insecticide:
none applied
Opti-Crop Test Information:
Location:
Carter Road, Owensboro, KY
Soil type and & drainage:
Henshaw silt loam; somewhat poorly drained
Conventional tillage:
ripped, disked, rolled, and cultipacked
Planting Date:
October 23, 1997
Varieties:
Becker and Clark
Fertilizer:
300 #/A 9:23:30 on September 26, 1997. N split twice in spring.
Fungicide:
Tilt at growth stage 10.3
Herbicide:
Roundup at planting time
Insecticide:
Warrior at 2.6 oz/A in both the fall and the spring
Wheat Tech Test Information:
Location:
Larry Thompson Farm, Allensville, KY
Soil type and & drainage:
Pembroke silt loam, well-drained
Conventional tillage:
disk ripped; disked and rolled twice
Planting Date:
October 20, 1997
Varieties:
Clark and Pioneer 2552
Fertilizer:
10 # N/A, 50 # P2O5/A, 50 # K20/A, and
10 # S/A on October 1, 1997.
50 # N/A on Feb. 9, 1998; 30 # N/A on March 6, 1998; and
35 # N/Aon April 2, 1998.
Fungicide:
Tilt near heading time in spring
Herbicide:
0.6 oz/A Harmony Extra on Nov. 12, 1997
Insecticide:
Warrior applied with Harmony
Results:
Table 1 shows percent residue cover, stand
establishment, and grain yields for the three tests we completed in the
1997-98 wheat season. Residue cover levels were consistently high under
no-till management. However, conventional tillage at the Lexington site
left considerably more corn residue on the surface than it did at the other
two sites. Stand establishment was reasonably good for no-till compared
with conventional tillage. Stands could have been a bit better at Lexington.
Yields were sharply depressed at Owensboro. Phil felt that hot temperatures
during grain fill, coupled with head scab, combined to hurt wheat yields
in his test. Head scab was a factor in the other two tests as well. Across
the three tests, no-till averaged 3.7 bushels/acre less than did conventional
tillage.
Location
Residue cover
Stand establishment
Grain yield
%
plants/sq. yd.
bushels/A
No-till Conv. till No-till Conv. till No-till Conv. till
Lexington
95
65
201 220
63.9 68.8
Owensboro
99
33
234 243
48.4 48.6
Allensville
98
34
270 234
71.4 77.5
Results are reported of a field and laboratory study on the influence of adult, coccinellid predators Coccinella septempunctata (L.) and braconid parasitoids Aphidius rhopalosiphi deStefani-Perez on the spread of barley yellow dwarf virus by bird cherry-oat aphid (Rhopalosiphum padi (L.)) and English grain aphid (Sitobion avenae (F.)).
Introduction:
Barley yellow dwarf (BYD) is the most
widespread and economically important disease of cereals world wide (Plumb
1983). Though BYD virus produces a disease in cereals, the disease epidemiology
is obligatorily dependent upon aphids for all movement and spatial development
(Irwin and Thresh 1990). Among the most important of these aphid vectors
are the bird cherry-oat aphid (Rhopalosiphum padi (L)) and grain
aphid (Sitobion avenae (F.)) (Mann et al. 1996).
In the UK a 'Decision Support System' is being developed to assist rationalization of spraying of autumn sown crops for control of the main aphid vectors (Harrington et. al. 1994; Mann et al. 1996) It has been suggested that natural enemies of the aphid vectors may affect aphid movement (Sopp et al. 1987; Knaust 1996) thereby influencing disease development and thus would need to be accounted for in the Decision Support System. Two common natural enemies of cereal aphids, the adult, coccinellid predator (Coccinella septempunctata (L.)) and the braconid parasitoid (Aphidius rhopalosiphi deStefani-Perez) were chosen for examination. In this communication the authors outline the experiment and present a preliminary view of a portion of the resulting data.
Methods and Materials:
All experiments were conducted at IACR-Rothamsted,
Harpenden, Hertfordshire, UK. A randomized complete block design with three
replications was repeated in the field twice during the autumn of 1996
and once in the laboratory during the winter 1996-97. Individual treatments
were applied as follows: no predator or parasitoid; a single predator;
a single parasitoid and a single predator plus a single parasitoid. Crop
plants used throughout this work were winter wheat Triticum aestivum
L. variety "Beaufort" and winter barley Hordeum vulgaris L. variety
"Puffin". Growth stages are reported in the format of Tottman and Broad
(1987).
All insects were reared in controlled environment (CE) rooms under a 16 hours : 8 hours (light : dark) cycle at ca. 60% RH. Aphids and coccinellids were held at a constant 18oC, while parasitoids were held at a constant 15oC. Six aphid colonies were maintained. Each of the two aphid species was maintained separately on BYDV-infected wheat and barley and non-BYDV infected barley. Two parasitoid colonies were maintained one for each aphid species. Seven spot ladybirds (C. septempunctata) were collected during September 1996 at Rothamsted Experimental Station and nearby. They were fed for one week by allowing them free choice in an aphid colony of appropriate species. They were then held in 9 cm disposable petri dishes at 4oC until needed. New aphids of the appropriate species were supplied to predator and parasitoid colonies from the aphid colonies reared on non-BYDV infected plants. In all predator and parasitoid colonies the aphid host was barley.
Forty eight, three-meter square plots of wheat and barley (24 plots each) were planted on 3 September 1996 utilizing standard agricultural practices with the exception that no insecticides were applied to either seed or plots. In each plot areas were identified for placement of cages. Ideally each area was two adjacent rows of 12 plants. Plants were checked for natural aphid infestation and any aphids were removed and the species, numbers and position of infested plants were recorded. Test plants were then covered with a 25 cm x 25 cm x 50 cm (length x width x height) mesh cage to prevent further colonization from wild aphid populations.
CE rooms were held at 10 hours : 14 hours (light : dark) and corresponding 14oC : 9oC temperature. Wheat and barley were sown in square, 25 plant grids at ca. 3 cm spacings in 53 cm x 53 cm x 5 cm (length x width x depth) trays. Each tray held 4 grids. At GS 12, 20 individual grids were covered using the same cages utilized in the field study.
On 18 September (GS 12, 20) the first field experiment was begun. Two plants, one each nearest the center of the two rows within a cage, were infested with 5 viruliferous fourth instar winged individuals of appropriate species. The aphids were confined to the plants using clip cages (Mann et al. 1995) and were held on the plants for five days. On 14 October (GS 12, 22-23) the second field experiment was begun. Aphid infestation was the same as the first experiment except that fourth instar non-winged individuals were used and confined on the plants in clip cages for only 24 hours. In the CE rooms caged plants (GS 12, 20) were infested with fourth instar apterae, using the same procedure as was utilized in the field trials except that all 10 aphids were in a single clip cage and only the center plant in each grid was infested. After 48 hours the clip cages were carefully removed.
One week before delivery into test cages ladybird beetles were removed from the cold storage and allowed "free choice" feeding on appropriate aphid species for 4 days, followed by 3 days of starvation. Three days prior to introduction into the test cages parasitoids were removed from the colony with an aspirator. They were held in 3 cm x 7.5 cm (diameter x length) glass bottles with net tops and fed a 50:50 mixture of honey : water on saturated Kimwipe®. On the day of introduction they were individually sexed and females were placed into small aspirators (Tamaki et al. 1970).
On the day of clip cage removal, predators and parasitoids were released into the cages during the afternoon. Predators were introduced into the cages by placing a 1.3 cm x 5 cm (diameter x length) uncapped glass vial containing one beetle in the center of the caged area. Parasitoids were delivered near the volumetric center of the cage via an aspirator.
In all experiments the predator / parasitoid treatments were maintained for two weeks. At the end of this period the aphids were counted and recorded by plant location, the cages were removed, and the plants sprayed with an insecticide to prevent further aphid movement. In the field trials test areas were sprayed every two weeks until plant leaf samples were taken for BYDV assay. In the CE room trial plants were sprayed immediately after cage removal and moved to a room that did not contain aphids and thereafter inspected to ensure that no aphids survived.
After the predator / parasitoid treatments were removed plants were allowed to grow for a further 5 weeks, after which a portion of the youngest completely unrolled leaf on the main stem was taken for analysis. The presence of BYDV MAV and PAV was confirmed by positive reaction with BYDV antiserum in enzyme-linked immunosorbent assay (ELISA).
Data were analyzed to test for differences in mean percent aphid infestation and mean percent virus infection resulting from the main effects 'Experiment' , 'Crop', 'Aphid Sp.' and 'Predator / Parasitoid Treatment'. Analysis was carried out using Statistical Analysis System (SAS Institute 1995). Percentages were analyzed by applying an analysis of variance (ANOVA) to square-root arcsin transformed data at the p= .05 level of significance. Results are reported as percentages.
Results & Discussion:
Tables 1, 2 and 3 summarize the mean percent
aphid infestations for field experiment 1, 2 and CE room respectively.
Preliminary statistical analysis indicated significant differences for
all main effects as follows; Experiment P = 0.0004, Crop P = 0.0001, Aphid
Sp. P = 0.0108, and Predator / Parasitoid Treatment P = 0.0017. However,
several significant interactions were also indicated. They are; Experiment
* Aphid Sp. P = 0.0001, Crop * Predator / Parasitoid Treatment P = 0.0179
and Aphid Sp. * Predator / Parasitoid Treatment P = 0.0328.
The first field experiment has greater overall values for infestation followed by the controlled environment experiment and then the second field experiment. This outcome might be expected solely on the basis of temperature. Temperatures in the first field experiment were warmer than in the second field experiment while the controlled environment room experiment was conducted at intermediate temperatures. It is also possible that plant size had an effect. The first field experiment and the controlled environment experiment were both started with "two leaf" stage plants while the second field experiment was at the "one to two tiller" stage. This later stage would have provided more leaf area per plant on which the aphids might settle and thus resulting in less need to move.
Barley plants tended to have higher infestation levels than wheat plants. This effect is constant across all three experiments, and both aphid species. Additionally, with one exception (See Table 2, second field experiment x R. padi x parasitoid), it is consistent within all predator / parasitoid treatments.
As of this writing all experimental plants have been subject to ELISA for detection of BYDV. However, analysis of the complete experiment is not yet available. The infection data reported here are from all three experiments, and include both barley and wheat but, only the aphid S. avenae, and the two natural enemies treatments: 'no predator or parasitoid', and 'single predator'. Initial ANOVA indicated significant differences between the three experiments. However, there was no significant difference between barley and wheat or between; 'no predator or parasitoid', and 'single predator'.
Percent virus infection for field experiments 1, 2 and CE room respectively were (mean ± standard error) 46.8 ± 4.1, 23.3 ± 3.7 and 30.3 ± 4.5 (n=12, F=8.92, P = 0.0013 ). Percent infection by crop was 37.0 ± 3.9 for barley and 29.9 ± 4.1 for wheat (n=18, P = 0.1250). Percent infections by treatments was; 'no predator or parasitoid' 31.1 ± 3.7 and 'single predator' at 35.9 ± 4.4 (n=18, P =0.3248). There were no significant three way interactions or two way interactions involving the factor 'Experiment'. However, there may be a two way interaction involving the factors 'Crop' and 'Treatment' (P = 0.0512).
Summary:
There was a significant different between
the overall mean percent virus infection in the three experiments. The
virus infection levels follow the same pattern as the aphid infestation
levels with the first field experiment having the greatest percent virus
infection, followed by the CE room experiment then the second field experiment.
There was no significant difference between crop type, however the barley
plots did produce a greater mean infection. The was no difference between
the two predator / parasitoid treatments.
Currently, the available percent aphid infestation and percent virus infection data do not provide evidence to indicate that natural enemies either reduce or enhance the level of BYDV. However, the reader is reminded that this is a very preliminary analysis. We suggest for example that the number of aphids present at the time of cage removal may prove to be a significant co-variate. Though two cages might have quite similar percent infestations they may be infested with very different numbers of aphids. Additionally this communication does not report any analysis of the spatial distribution of either aphid infestation or virus infections, which will be examined later.
References:
Harrington, R., Mann, J.A., Plumb, R.T.,
Smith, A.J., Taylor, M.S., Foster, G.N., Holmes, S.J., Masterman, A.J.,
Tones, S.J., Knight, J.D., Oakley, J.N., Barker, I., & Walters, K.F.A.,
1994. Monitoring and forecasting for BYDV control - the way forward? Aspects
Applied Biology. 37:197-206.
Irwin, M. & Thresh, J. M., 1990. Epidemiology of barley yellow dwarf: A study in ecological complexity. Annual Review Phytopathology 28:393-424.
Knaust, H.J., 1996.Untersuchungen zur sekundaren ausbreitung von getreideblattlausen und deren bedeutung fur die epidemiologie des BYD-virus. Hannover Univ. Ph. D. Diss. Cuvilier Verlag, Gottingen. 205pp
Mann, J.A., Tatchell, G.M., Dupuch, M.J., Harrington, R., Clark, S.J. & McCartney, H.A., 1995. Movement of apterous Sitobion avenae (Homoptera: Aphididae) in response to leaf disturbances caused by wind and rain. Annals Applied Biology 125:417-427.
Mann, J.A., Harrington, R., Morgan, D., Walters, K.F.A., Barker, I., Tones, S. & Foster, G.N., 1996. Towards decision support for control of barley yellow dwarf vectors. Proceedings Brighton Crop Protection Conf - Pests & Diseases. 1995, 179-184.
Plumb, R.T., 1983. Barley yellow dwarf virus - a global problem. In Plant Virus Epidemiology. ed. R.T. Plumb, J.M Thresh, pp. 185-98. London: Blackwell Sci 377 pp.
SAS Institute. 1995. SAS procedure guide for personal computers Ver. 6, ed. SAS Institute, Cary, NC. 1996.
Sopp, P.I., Sunderland, K.D. & Combes, D.S., 1987. Observations on the number of cereal aphids on the soil in relation to aphid density in winter wheat. Annals Applied Biology 111:53-57.
Tamaki, G., Halfhill, J.M. & Hathaway, D.O., 1970. Dispersal and Reduction of Colonies of Pea Aphids by Aphidius smithi (Hymenoptera: Aphidiidae). Annals Entomological Society America 63:973-980.
Tottman, D.R. & Broad, H., 1987. Decimal code for the growth stages of cereals. Annals Applied Biology 110:683-687.
Acknowledgements:
We thank all colleagues in the Rothamsted
Insect Survey who braved the foul weather conditions while they lay prostrate
counting aphids. IACR receives grant-aided support from the Biotechnology
and Biological Sciences Research Council of the United Kingdom. The senior
author thanks the University of Kentucky, the Kentucky Small Grain Growers
Association, Zenica Ag Products and Gustafson Inc. for support during my
sabbatical year.
| Crop | Barley | Wheat | ||
| Aphid | R. padi. | S. avenae | R. padi | S. avenae |
| Treatment* | ||||
| None | 35.0 ±12.0 | 51.0 ±12.0 | 31.6 ± 10 | 44.0 ± 9.0 |
| Predator | 17.0 ± 0.0 | 60.0 ±16.0 | 12.5 ± 3.0 | 16.0 ± 9.0 |
| Parasitoid | 38.0 ± 16.0 | 56.0 ± 17.0 | 33.0 ± 17.0 | 57.0 ± 14.0 |
| Both | 25.0 ± 5.0 | 73.0 ± 2.0 | 6 .4 ± 5.0 | 39.0 ± 9.0 |
| Aphid Sp. | 30.3 ± 6.0 | 59.3 ± 6.5 | 18.6 ± 5.0 | 39.6 ± 6.3 |
| Crop | 45.5 ± 5.4 | 30.1 ± 4.6 | ||
| Experiment | 37.6 ± 3.7 | |||
| Crop | Barley | Wheat | ||
| Aphid | R. padi. | S. avenae | R. padi | S. avenae |
| Treatment* | ||||
| None | 39.8 ± 11.8 | 34.2 ± 4.4 | 38.4 ± 8.2 | 18.3 ± 2.5 |
| Predator | 48.6 ± 6.4 | 31.0 ± 8.0 | 9.1 ± 6.9 | 2.8 ±1.3 |
| Parasitoid | 36.0 ± 4.2 | 31.3 ± 6.3 | 38.1 ± 10.6 | 22.5 ± 4.5 |
| Both | 35.8 ± 16.7 | 25.5 ± 3.9 | 17.3 ± 9.1 | 15.6 ± 4.2 |
| Aphid Sp. | 40.1 ± 4.9 | 30.5 ± 2.7 | 25.7 ± 5.4 | 14.5 ± 2.8 |
| Crop | 35.1 ± 2.9 | 20.3 ± 3.3 | ||
| Experiment | 27.9 ± 2.4 | |||
| Crop | Barley | Wheat | ||
| Aphid | R. padi. | S. avenae | R. padi | S. avenae |
| Treatment* | ||||
| None | 40.0 ± 4.6 | 37.3 ± 2.7 | 28.0 ± 8.3 | 30.7 ± 10.9 |
| Predator | 47.0 ± 4.4 | 40.5 ± 3.8 | 46.7 ± 4.8 | 36.0 ± 10.1 |
| Parasitoid | 48.0 ± 6.1 | 51.9 ± 11.6 | 39.7 ± 13.9 | 61.3 ± 1.3 |
| Both | 28.7 ± 13.4 | 44.0 ± 10.0 | 17.8 ± 3.4 | 4.8 ± 8.4 |
| Aphid Sp. | 41.0 ± 4.1 | 43.4 ± 3.8 | 33.0 ± 5.9 | 43.2 ± 5.1 |
| Crop | 42.2 ± 2.7 | 38.1 ± 3.6 | ||
| Experiment | 40.1 ± 2.5 | |||
Making
No-Till Wheat Production Profitable:
Corn Hybrid Selection
Morris J. Bitzer, Larry J. Grabau,
and Colleen Steele
Department of Agronomy
Forty eight corn hybrids from the 1997 Kentucky Hybrid Corn Performance Tests were screened to determine their harvest index, amount of residue and grain yield. Harvest index is the ratio of grain yield to total biomass yield. The earlier maturing hybrids had lower average harvest index values than the later maturing hybrids. From these 48 hybrids, 12 corn hybrids were selected for double cropping with no-till wheat. These 12 hybrids included 5 early, 6 medium and 1 late maturing hybrid. These 12 hybrids were grown and evaluated for harvest index and grain yield in 1998. Two wheat varieties were no-till seeded into the residue shortly after the corn hybrids were harvested. Stand counts were taken of the wheat after it had completely emerged. There were very small differences between stand counts and corn hybrids which the wheat had been seeded into the residue from the corn. The stand counts ranged from 23.7 to 30.1 plants per square foot.
Introduction:
Corn residue helps reduce topsoil erosion
in no-till wheat systems. However, that same corn residue can greatly complicate
stand establishment for no-till wheat, may also reduce N availability and
increase problems with winter survival. It is well known that corn hybrids
differ in their yield potential. Kentucky farmers have naturally chosen
to grow corn hybrids with the best possible yield potential. What is not
known, however, is whether the high yielding corn hybrids all leave behind
similar amounts of residue. In fact, a corn hybrid which yields slightly
less but will substantially less residue might be a good hybrid to use
for a no-till wheat management system. Therefore, it would be beneficial
to Kentucky farmers considering no-till wheat systems to have information
on how the available corn hybrids differ in residue amounts in relation
to their grain yield. This study is designed to identify a set of corn
hybrids which might work well in no-till wheat systems.
Materials and Methods:
In the fall of 1997, the 132 hybrids in
the 1997 University of Kentucky Hybrid Performance Tests were evaluated
at 2 locations to select 48 hybrids for biomass, yield and harvest index.
These 48 hybrids were selected on the basis of potential low biomass (visual
observation) in each maturity group (early, medium and late). From the
results of these 48 hybrids, 12 hybrids were selected to plant in the spring
of 1998. The maturity of this group of 12 hybrids were 5 early maturity
(less 112 days), 6 medium maturity (113-117 days) and 1 late (118 or more).
The one late hybrid was selected as a check to compare for high yield,
low harvest index and a higher amount of residue than the other hybrids.
These 12 hybrids were planted in a 4 replicated randomized complete block
design. At maturity, they were hand harvested for yield (40 feet of row
of each hybrid was harvested and weighed). A separate whole plant sample
(8 plants) was cut and weighed for biomass yield. The remainder of each
plot was machine harvested and the residue evenly distributed on each plot.
Five weeks after harvest, the two wheat varieties, Pioneer 2552 and Foster
were no-till drilled at 35 seeds per square foot of row into one-half of
each plot at the optimum time for wheat seeding (Oct. 14). Wheat stand
counts (2 rows-.5m long) were taken on November 12.
Results and Discussion:
The data obtained on the 12 corn hybrids
is shown in Table 1. In 1997, the early and medium maturity hybrids selected
were the higher yielding hybrids with lower residue and higher harvest
index values than the other hybrids from which they were selected. The
late maturing hybrid was a high yielding hybrid with a high amount of residue
and a low harvest index. All of the later maturing hybrids had high levels
of residue and low harvest indexes. If the amount of residue or high harvest
index is a reliable measure for obtaining better no-till wheat stands,
then these hybrids selected should give an indication of this.
In 1998, the values obtained and the lack of a significant difference in stand counts did not support this hypothesis. The values were very inconsistent as to stand counts and there appeared to be no relationship between stands and amount of residue or harvest index. The main thing that can be denoted from this data is that the selection of an earlier maturing, high yielding hybrid will result in less residue, a slightly higher harvest index and good wheat stands than that obtained from later maturing hybrids. One of the reasons that this data may have been somewhat inconsistent was that very poor johnsongrass control was obtained in the plots. The competition from the johnsongrass somewhat reduced the differences in the height of the different hybrids thus making the residue values less reliable. The late maturing hybrid was not any different in height or total biomass than several of the earlier maturing hybrids. If residue is a problem when establishing wheat stands, selecting a high yielding, early-medium or early maturing hybrid should reduce the amount of residue left in the field.
1. Akin
A6460
143 7627
51.5
162 7686
50.1
30.0
2. Crow's
496
146 6848
54.5
172 7800
51.1
27.0
3. DeKalb
DK626
150 7298
55.1
149 7501
48.7
23.6
4. Pioneer
3394
154 8087
51.7
152 6329
53.4
27.0
5. So.
States SS676
141 7774
50.5
153 6828
51.9
29.6
Medium Yellow Hybrids
6. Cargill
6888
143 6588
54.9
150 7214
50.0
26.9
7. Caverndale
CF840 143
6816 54.0
167 7721
50.7
27.5
8. DeKalb
DK642
146 7385
52.9
159 8245
47.8
30.1
9. Great
Lakes 6631 152
7691 52.6
167 7138
52.6
27.0
10. Mycogen 2815
149 7095
54.0
171 8341
49.2
27.6
11. NK Brand N73-Q3
145 7531
51.9
149 6380
52.4
25.2
Late Yellow Hybrid
12. So. States SS943
162 9528
48.7
177 8080
51.1
26.8
_______________________________________________________________________
L.S.D. (0.10)
10
NS
NS
15 1294
5.3
NS
_______________________________________________________________________
1Harvest index
= grain yield/total biomass
2Stand counts
are number of plants per square foot, average of 2 varieties.
Comparative
Performance of Wheat Varieties in
No-Till and Conventional-Till
Trials
Charles Tutt, Dave Van Sanford, and
Sandy Swanson
Department of Agronomy
Research Objective:
To determine whether wheat varieties that
are superior under conventional tillage are also superior under no-tillage.
Methods:
| Location: | Logan County | Shelby County |
| Cooperator: | Walnut Grove Farms | W. & D. Ellis Farms |
| Previous Crop: | Corn | Corn |
| Conventional Tillage: | Disk-ripper, Disk, Cultipacker | Chisel Plow, Disk |
| Stubble Condition (no-till): | Mowed | Standing stubble |
| Planting Date: | October 8, 1997 | October 1, 1997 |
Entries consisted of 46 commercial and public soft red winter wheat varieties available to Kentucky's wheat farmers. There were 4 replications of each variety at each location. Conventional tests were planted with a 6-row cone seeder with double-disc openers and a row spacing of 7". No-till plots were seeded with a 7-row cone seeder equipped with John Deere 750 openers and a row spacing of 7.5". Seeding rates were approximately 325 seeds/sq.yd. for conventional tillage and 365 seeds/sq. yd. for no-till plots. Inputs were similar to those used by the cooperating farmers on their commercial wheat fields.
Results:
Variety yield means and rankings are presented
in the following two tables.
Conclusion:
The correlation of rankings at each location
was almost identical: 0.62 at Shelby Co. and 0.61 at Logan Co. In general,
varieties that performed well under conventional tillage also fared well
under no-till. If there was perfect agreement between conventional and
no-till, this value would be 1.0. There were cases, however, where the
agreement between the two systems was poor. In Logan Co., Pioneer Brand
25W33 ranked 5th under conventional, 21st under no-till.
Glory ranked 7th under conventional, 31st under no-till,
and Pioneer Brand 2552 which ranked 24th under conventional,
was 3rd under no-till. At Shelby Co., there was less dramatic
disagreement between the two systems, but there were exceptions like NK
Coker 9704: 40th under conventional, 14th under no-till.
The jury is still out on the role of variety in adopting a no-till wheat
production system. This report should be considered an update, and not
the final word.
Objectives:
1. To identify scab resistance in adapted
varieties and breeding lines.
2. To develop field-based procedures for resistance screening that can be incorporated into our breeding program.
Methods:
Entries in the 1998 Uniform Winter Scab
Nursery along with a number of advanced breeding lines (Tables 1, 2) were
planted in a randomized complete block design with three replications near
Lexington, KY. Experimental units were small plots (20 ft2)
with 6 rows planted in 7" rows using a Hege headrow planter. The planting
date was 21 Oct. 1997. The previous crop was corn (Zea mays L.)
and the seedbed had been chisel plowed and disked. Input applications were
made according to UK recommendations.
Our inoculation procedure was as follows: Mason jars containing 500 g of corn seed were inoculated with the head scab fungus (Fusarium graminearum). About 10 days before heading, we spread 225 g of corn/plot among the wheat rows. Beginning just prior to flowering and continuing through early grain fill, the plots were mist-irrigated for approximately 1 hour morning and evening. Symptoms were measured at approximately 19 days after flowering. Incidence of scab in 4 row-feet (two 2' rows) was estimated by recording the number of heads showing typical scab symptoms. Severity was estimated by counting scabby florets on 5 random heads per plot. The two 2' rows were harvested with a sickle, total head number was counted, and grain was threshed in a single head thresher to estimate % scabby seed. Remaining plots were harvested with a Hege plot combine to measure grain yield and test weight.
Results:
Scab symptoms and other data are presented
in the Tables 1-3.
Conclusions:
At this stage in our research our only
conclusions are that there appear to be differences in resistance to head
scab among adapted varieties and breeding lines in our program. At this
point, under heavy disease pressure from inoculation, none of the varieties
or breeding lines looks very good in terms of resistance. We don't yet
know whether our disease pressure is too heavy to prevent us from seeing
moderate levels of resistance. One way to answer this question is to establish
a baseline level of natural infection with which we could compare our inoculated
plots (Table 3). The low correlation (r=0.22) between inoculated and control
plots for % scabby seed indicates that disease levels under inoculation
may be higher than under natural infection. We will focus on this problem
in the coming year.
