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2001
STEEP III Progress Report
- RESEARCH PROJECT
TITLE: New Technologies and Strategies for Managing Weeds in Conservation
Cropping Systems for Dry Land Wheat
INVESTIGATORS:
Frank Young, USDA-ARS Pullman, WA, Agronomy & Weed Science; Donn
Thill, University of Idaho, Weed Science.
INTERIM OR FINAL
REPORT: Interim except final report for objective IIa
PROJECT OBJECTIVES:
- Objective I:
Determine the impact of farming practices and systems on soil, air,
and water quality. Assess the impacts of conservation practices on soil,
water, and air quality and use this information to develop tools for
improved conservation planning and resource management.
- Objective II:
Develop new technologies and increase efficiency of inputs that improve
profitability of conservation farming systems. Develop profitable and
environmentally sound conservation practices for pest and plant nutrient
management. Identify crop plants and plant characteristics that enhance
conservation farming systems for specific agronomic zones. Develop profitable
conservation tillage and cropping systems for lands most vulnerable
to resource degradation.
- Objective IIa:
Determine effectiveness of different herbicides for control of volunteer
herbicide-resistant crops (HRC); Roundup Readyâ spring wheat and
canola, Clearfieldâ wheat and canola, and Liberty Linkâ
canola.
- Objective III:
Assess the profitability of conservation tillage and cropping systems
for lands most vulnerable to resource degradation. Estimate profitability,
risk, and other economic impacts of conservation farming systems.
- Objective IV:
Accelerate grower evaluation and adaptation of profitable conservation
systems.
KEY WORDS:
Herbicide-resistant crops (HRC), Roundup (glyphosate).
STATEMENT OF
PROBLEM: Weeds often pose the single greatest threat to successful
adoption of direct-seed, conservation cropping systems. With current
herbicide technology, weeds such as jointed goatgrass, feral rye, and
downy brome are difficult or impossible to selectively control in winter
wheat. In spring crops, especially broadleaf crops, Russian thistle
is the major threat. Herbicide-resistant crop development is progressing
rapidly and providing an opportunity to selectively control these and
other weeds in direct-seed cropping system. However, there is little
or no information on how to safely and effectively incorporate them
into Pacific Northwest (PNW) direct-seed dry land winter wheat cropping
systems. Important, unanswered questions include which HRC crops should
or should not be used in a particular cropping system, and if used,
how often. Many of the herbicides used on HRC are currently used or
are closely related to herbicides used in PNW wheat production. Thus,
how best to control volunteer herbicide resistant crops in these situations
also requires study. Traditionally, growers have relied on Roundup to
control volunteer crops and weeds in no-till cropping systems. This
poses a problem for control of volunteer HRC such as Roundup Ready wheat
and canola.
ZONE OF INTEREST:
winter wheat-fallow and annual crop in low, intermediate and high rainfall.
ABSTRACT OF
RESEARCH FINDINGS:
Studies were established in spring 2000 and 2001 near Moscow, ID at
the University of Idaho Parker Research Farm and near Ralston, WA at
the no-till spring cropping systems study site to evaluate alternatives
to traditional Roundup treatments for control of volunteer HRC. Roundup
Ready spring wheat (RRW), Roundup Ready canola (RRC), Clearfield wheat
(CFW), Clearfield canola (CFC), and Liberty Link spring canola (LLC)
were seeded with a no-till drill to simulate volunteer HRC. At 14 days
after treatment (DAT) RRW was controlled 93% by Gramoxone Extra + Direx.
By 21 DAT control was best (90 to 95%) with Gramoxone Extra + Direx
and treatments containing Select or Assure II. At 21 DAT, CFW was controlled
93 to 97% by Assure II, Select, Gramoxone Extra + Direx , Touchdown
IQ, and all Roundup treatments except Roundup in combination with Rely
or Gramoxone Extra (66 to 79% control). RRC was controlled 98% by Gramoxone
Extra + Direx 28 DAT. At 28 DAT, control of CFC and LLC ranged from
94 to 98% with Gramoxone Extra + Direx , Touchdown IQ, and all Roundup
Ultra RT treatments except Roundup Ultra RT in combination with Rely
(CFC only) or Gramoxone Extra (67 to 88% control). The crop growing
season of 2000-2001 was a transition year between Phase I and Phase
II of the no-till spring cropping system study at Ralston. It was tremendously
dry, receiving only 7.2 inches of rainfall from September 1, 2000 to
August 31, 2001. Because this growing season was transitional, final
cropping systems for Phase II were based on this year's logistics.
RESULTS AND
INTERPRETATION:
Objective I: Crop
rotations to be examined in Phase II selected for the main core site
include three rotations compared to the traditional reduced tillage
winter wheat fallow system. These rotations include a) no-till hard
red spring wheat; b) no-till hard red spring wheat/spring barley; and
c) no-till facultative spring wheat/no-till spring canola. Hard red
spring wheat will entail using a variety (Tara) that has host-plant
resistance to Hessian fly, a major pest of no-till spring wheat. Hard
red spring wheat plots will be split in half and compare grain production
and quality of normal inputs with reduced inputs. Phase II cropping
systems include: a) three-year crop rotation of no-till winter wheat,
spring triticale, spring wheat; b) no-till hard white spring wheat,
no-till spring canola; and c) one-pass light tillage of spring wheat,
spring canola. Yields this year were very low and all broadleaf crops
(canola and mustard) were generally unharvestable. A combination of
drought during the growing season, low over-winter soil moisture recharge,
and damaging frost on May 31 prevented even average crop yields. Winter
wheat yield was 33 bu/A compared to the previous 5-yr average of 62
bu/A. Hard red spring wheat yield ranged from 8 (15.2% protein) to 16
bu/A (15.9% protein) compared to the previous 5-yr average of 36 bu/A
(>14%).
- Objective II:
For the second year in a row, plots were established to compare Surefire®
and Roundup®, plus 2,4-D applied with a broadcast sprayer and a
new applicator to reduce pesticides for the postharvest control of Russian
thistle. Control of Russian thistle with Surefire® was >95% regardless
of sprayer technology. Because this system was successful, the reduced
pesticide applicator was used on one treatment of the main core cropping
systems study. Control using Surefire® was >90% and cost and
pesticide usage was reduced more than 60%.
The project was
requested by WSU administrators to abandon Roundup® Ready®
spring wheat experiments. Because of the turmoil and discontent surrounding
the use of Roundup® Ready® spring wheat on growers fields,
the separate long-term study evaluating a HRC rotation of Roundup®
Ready® spring wheat and Liberty Link® canola was changed.
In lieu of this system, the use of Roundup® Ready® canola
has been inserted into the main plot trials.
- Objective IIa.
Plots of Roundup Ready spring wheat and canola, Clearfield wheat and
canola, and Liberty Link canola were planted at 20% the normal seeding
rates (canola was seeded at 100% in 2001 due to poor emergence and stand
counts the previous year) into standing wheat stubble to simulate volunteer
crops near Ralston, WA at the USDA Ralston Direct Seeding Project Site
and near Moscow, ID at the University of Idaho Parker Research Farm
in spring 2000 and 2001. Herbicide treatments were applied when the
wheat was in the 5 to 6 leaf stage and when the canola was 2 to 4 inches
in diameter. Control was evaluated visually at 14 and 21 days after
treatment (DAT). Herbicide treatments were Roundup Ultra RT, Landmaster
BW, Fallowmaster, Gramoxone Extra, Rely, Touchdown IQ, Roundup Ultra
RT + Rely, Roundup Ultra RT + Gramoxone Extra, Gramoxone Extra + Direx,
Assure II, Assure II + Roundup Ultra RT, Select, Select + Roundup Ultra
RT, and an untreated control (Table 1). Above ground biomass was collected
from a 2.7 ft2 area in each plot 28 DAT. Canola biomass was not collected
at Ralston in 2000 due to inconsistent emergence and poor stand. Studies
were terminated immediately after biomass collection to prevent seed
production.
At 14 DAT, Roundup
Ready wheat was controlled 93% by Gramoxone Extra + Direx (Table 2).
By 21 DAT control was 90 to 95% with Gramoxone Extra + Direx and all
treatments containing Assure II or Select. On average these treatments
reduced biomass 95% compared to the untreated control. As expected,
treatments containing glyphosate did not control volunteer Roundup
Ready wheat. Gramoxone Extra or Rely, alone or mixed with Roundup
Ultra RT, also did not control volunteer Roundup Ready wheat.
Control of Clearfield
wheat ranged from 89 to 97% with Roundup Ultra RT, Gramoxone Extra
+ Direx, Touchdown IQ, Landmaster BW, Fallowmaster, Assure II + Roundup
Ultra RT, and Select + Roundup Ultra RT 14 DAT (Table 3). By 21 DAT
Assure II, Select, and the previously listed treatments controlled
volunteer Clearfield wheat 93 to 97 %. Biomass was reduced on average
96% by Roundup Ultra RT, Assure II, Assure II + Roundup Ultra RT,
Select, Select + Roundup Ultra RT, Gramoxone Extra + Direx, Touchdown
IQ, Landmaster BW, and Fallowmaster. Gramoxone or Rely did not control
volunteer Clearfield wheat.
At 14 DAT, Roundup
Ready canola was controlled 92% by Gramoxone Extra and 97% by Gramoxone
Extra + Direx (Table 4). By 21 DAT, control had dropped slightly with
Gramoxone Extra due to re-growth, but control with Gramoxone Extra
+ Direx was consistent at 98%. Biomass was reduced most by Gramoxone
Extra + Direx, but due to a large degree of variation it was not significantly
different than Roundup Ultra RT + Gramoxone, Gramoxone, and Landmaster
BW. All other treatments did not control volunteer Roundup Ready Canola.
Control of Clearfield
canola was 91% or greater with all treatments except Rely, Roundup
Ultra RT + Rely, Assure II, and Select 14 DAT (Table 5). At 21 DAT,
control was best with Roundup Ultra RT (96%), Landmaster BW (98%),
Fallowmaster (98%), Touchdown IQ (94%), Gramoxone Extra + Direx (97%),
Assure II + Roundup Ultra RT (96%), and Select + Roundup Ultra RT
(95%). These treatments reduced biomass 96% on average. All other
treatments did not control volunteer Clearfield Canola.
At 14 DAT, all treatments except Rely, Assure II, and Select controlled
Liberty Link canola 92% or more (Table 6). By 21 DAT control was best
with Roundup Ultra RT (95%), Landmaster BW (98%), Fallowmaster (98%),
Touchdown IQ (95%), Roundup Ultra RT + Rely (93%), Gramoxone Extra
+ Direx (95%), Assure II + Roundup Ultra RT (97%), and Select + Roundup
Ultra RT (96%). Roundup Ultra RT, Landmaster BW, Fallowmaster, Gramoxone
Extra, Touchdown IQ, Roundup Ultra RT + Rely, Roundup Ultra RT + Gramoxone
Extra, Gramoxone Extra + Direx, Assure II + Roundup Ultra RT, and
Select + Roundup Ultra RT reduced biomass by 80% or more.
INTERACTION
WITH OTHER SCIENTISTS CONDUCTING RELATED RESEARCH: Dan Ball, OSU
Weed Scientist, Pendleton, OR and Joe Yenish, WSU Extension Weed Scientist,
Pullman, WA have also conducted studies to evaluate the effectiveness
of different herbicides for control of volunteer Roundup Readyâ
spring wheat in no-till cropping systems.
PUBLICATIONS,
REPORTS, AND PRESENTATIONS:
Rainbolt, C. R.,
D. C. Thill, D. A. Ball, J. P. Yenish, and F. L. Young. 2001. Managing
volunteer following herbicide resistant crops. Herbicide resistant crops
symposium. Proc. of Western Soc. Weed Sci. 54:90.
Rainbolt, C. R.,
D. C. Thill, D. A. Ball, J. P. Yenish, and F. L. Young. 2001. Managing
volunteer after herbicide resistant crops. Proc. Northwest Direct Seed
Cropping Systems Conf. p. 115-123.
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