National Jointed Goatgrass Research Program

 

Progress Report-2002

NOTICE
The following is a progress report containing preliminary data and results that may be modified by future research.
Please contact the listed authors
or Extension Coordinator for additional information.

 

TITLE:  Best Management Practices for Control of Jointed Goatgrass in Winter Wheat in the Intermountain States

PRINCIPAL INVESTIGATORS:

John Evans, Weed Scientist, Utah State University
Don Morishita, Weed Scientist, University of Idaho
Paul Patterson, Ag. Economist, University of Idaho 

TIME LINEJuly 1, 2000 to June 30, 2005.  On schedule.

 

ORIGINAL HYPOTHESIS:  Crop rotations, herbicide-resistant cultivars, and improved planting technologies are presently available to winter wheat producers which improve jointed goatgrass management and increase profit margins compared to traditional winter wheat-fallow systems in the intermountain region.

 

SUMMARY OF PROGRESS:  The underlying goal of these studies is to evaluate several Best Management Practices (BMPs) in the intermountain region.  The first full-year cycle of a six-year study was completed with the 2001 crop harvest and the results established baselines for jointed goatgrass stand densities and crop yield.  Initial results verify the positive role played by inserting a spring crop into the winter wheat-fallow rotation.  Safflower draws upon soil moisture and fertility not used by wheat and can be grown immediately after wheat in the rotation to provide an additional cash crop.  Some jointed goatgrass remained in wheat in this modified rotation but it demonstrated very high susceptibility to imazamox when an herbicide-resistant wheat, CV9804, was substituted for the traditional varieties grown in the region.  Economic estimates of the BMPs reveal that growers will not be penalized by the alternative rotation due to recovered yields of wheat and the added safflower crop during a six-year interval.

 

OBJECTIVES:

Develop BMP recommendations to control jointed goatgrass in the intermountain dryland winter wheat growing areas.

Determine the degree that amended crop rotations, employing safflower, spring wheat, and BMPs, manage jointed goatgrass infestations in subsequent wheat crops.

Compare BMPs with a separate conjoint study of the efficacy of using an imidazolinone-resistant winter wheat cultivar to control jointed goatgrass.

Provide economic analysis of BMPs compared to traditional cultural practices and contribute to and test the effectiveness of the jointed goatgrass bioeconomic model.

 

EXPERIMENTAL DESIGN:

Two test sites with natural jointed goatgrass populations, one in southern Idaho and one in Utah, were selected.  BMPs to be investigated and evaluated include: amended crop rotations utilizing safflower and/or spring wheat, variable tillage, earlier crop planting date, more competitive cultivar, and use of imidazolinone-resistant winter wheat cultivar.  A comparison between traditional crop rotation sequence of winter wheat-fallow-winter wheat versus winter wheat-safflower-fallow and/or winter wheat-spring wheat-fallow for a minimum of five years are planned.  The producers are responsible for planting, fertilizing, and tillage.  Researchers conduct spraying and harvest seed with a harvester equipped to take seed samples for test weight, yield, quality, and dockage.  When sufficient data is collected an economic analysis of BMPs, with amended rotations, will be conducted and compared to traditional cultural practices in use in each site area.  Information collected can be used for contributing to and testing of the jointed goatgrass bioeconomic model.

UTAH LOCATION.  Fields with high potential for jointed goatgrass infestation at the Blue Creek Experiment Station in northern Utah provide opportunity to compare traditional winter wheat-fallow-winter wheat rotations, with jointed goatgrass best management strategies including safflower-fallow-winter wheat rotation possessing measurably different annual grassy weed management capacity (Table 1).  Plots are 40 x 300 feet, with three replications.

Table 1. Comparing rotations of winter wheat-fallow-winter wheat and safflower-fallow-winter wheat.

 

Year

Rotation

2000

2001

2002

2003

2004

2005

     11

Wheat

Fallow

Wheat

Fallow

Wheat

Fallow

     2

Safflower

Fallow

Wheat

Safflower

Fallow

Wheat

1Plots with traditional wheat-fallow-wheat rotation.

Wheat cultivars used are standard winter wheat varieties adapted for the area.

Imidazolinone-resistant winter wheat (CV9804), treated with imazamox, is compared with the best available competitive winter wheat variety to manage jointed goatgrass in a winter wheat-fallow-winter wheat rotation (Table 2).  Treatments are replicated three times with plot size of 40 x 300 feet.

Table 2. Replacing standard winter wheat with an imidazolinone-resistant winter wheat, CV 9804, with or without imazamox  treatment to manage jointed goatgrass.

 

Year

Rotation

2000

2001

2002

2003

2004

2005

     11

Fallow

Wheat

Fallow

Wheat

Fallow

Wheat

     3

Fallow

CV98042

Fallow

CV98042

Fallow

CV98042

     3a

Fallow

CV9804

Fallow

CV9804

Fallow

CV9804

1Plots with traditional wheat-fallow-wheat rotation.

2CV9804 wheat with application of imazamox herbicide

Wheat cultivars used are standard winter wheat varieties adapted for the area.

 

IDAHO LOCATION.  A naturally infested field located south of Rockland, Idaho compares traditional winter wheat-fallow-winter wheat rotations to continuous spring wheat and winter wheat-safflower-fallow rotations for jointed goatgrass management.  Similar to the Utah experiments, three replications are used and each phase of the rotations will be present each year.  Individual plots are 40 by 350 feet.

Until imidazolinone-resistant spring and winter wheat seed becomes available in Idaho from the UI wheat-breeding program, ClearfieldTM (CV9804) will be planted alongside treatments outlined above to determine the value of imazamox herbicide for selective jointed goatgrass control in wheat.

PROGRESS:

UTAH CONTRIBUTION: A previously completed five-year investigation of integrated methods to eliminate jointed goatgrass from ensuing winter wheat crops in the Intermountain region revealed that inserting a spring crop like safflower was the best option.  Safflower is the preferred alternative to wheat because it’s agronomic production and culture is very similar to wheat regarding planting and harvesting equipment, fertility and moisture needs, and generally preferred crop habitat.  Further, the rotation can be abbreviated to provide one additional crop year in each six-year interval where summer fallow is required for sustained production.  The modified rotation employed as a major component of the jointed goatgrass control in the Intermountain region is safflower-fallow-winter wheat.  This rotation is measured against the traditional winter wheat-fallow-winter wheat practiced for decades in the area.  Table 3 reveals jointed goatgrass densities in crop and wheat yields from one complete rotation cycle comparing the two alternative rotations at the beginning of a six-year cycle. 

 

Table 3.  Jointed goatgrass densities and winter wheat yields following one complete cycle of winter wheat-fallow-winter wheat rotation versus safflower-fallow-winter wheat.

Rotation

JGG

Wheat yield

 

Numbers/m2

---bu/A---

 

 

 

 

Wheat/fallow/wheat

68.3

43.0

Safflower/fallow/wheat

2.7

42.2

LSD 0.05

61

NS

 

Winter wheat yield did not measurably differ between the two rotations examined, apparently sufficient moisture and nutrients were available for wheat yields that were near the twenty year average for the area.  Jointed goatgrass reproductive tillers at harvest increased alarmingly to 68.3 tillers/m2 in 2002 in the winter wheat-fallow-winter wheat plots compared with less that 2 tillers/m2 recorded in the crop in 2000.  On the other hand, jointed goatgrass reproductive tillers recorded in wheat was only 2.7 tillers/m2 in the safflower-fallow-winter wheat regime, a twenty-five fold decrease in weed stand attributable to the altered rotation.  The numbers of jointed goatgrass reproductive tillers varied widely among the four sub-samples counted in each of the three replications and is responsible for the extremely large LSD.05 value over 60.

 

Winter wheat following safflower in the modified rotation exhibited small numbers of jointed goatgrass tillers in the crop at harvest suggesting that herbicide-resistant cultivars may be needed to eventually eliminate this weedy grass in rain-fed winter wheat production in the Intermountain region.

 

In 2001, we presented a comparison of jointed goatgrass densities and winter wheat yields between a standard wheat variety and an imidazolinone-resistant cultivar (CV9804), with and without postemergence treatment of imazamox (Table 4).  Although CV9804 was not developed as an adapted cultivar for this area, yields were reasonably similar to a standard type and jointed goatgrass reproductive tillers were reduced to zero when CV9804 was treated with imazamox at .047 lb ai/A. CV9804 treated with .047 lb ai/A imazamox expressed no visible injury symptoms, but the yield of this treatment was lower than non-treated wheat.  Jointed goatgrass was measurably lower in imazamox treated CV9804 than in non-treated wheat.

 

Table 4.  Wheat yields and jointed goatgrass densities recorded in 2001 in wheat with and without imazamox treatment. Blue Creek, UT

 

Herbicide rate

JGG

Crop injury

Yield

 

oz/A

Number/m2

---%---

bu/A

 

 

 

 

 

Standard variety

-

3.9

0

45.9

CV9804

0

5.0

0

41.9

CV9804 +

 

 

 

 

  imazamox

6

0

0

39.8

LSD 0.05

 

2.1

-

5.9

Field space at the Blue Creek station did not provide opportunity to repeat treatments contrasting a standard wheat variety against CV9804 with and without imazamox, to provide a wheat harvest every year.  Consequently, these comparisons were in fallow in 2002 and whether the herbicide-resistant wheat will demonstrate the distinct advantage over untreated traditional wheat recorded in Table 4 cannot be substantiated until the 2003 winter wheat harvest.

IDAHO CONTRIBUTION:

The second cropping year of a five-year trial was completed in 2002. This trial is located in Power County, Idaho on a commercial wheat-fallow dryland farm. Winter wheat ('Sprague') was seeded in September 28, 2001, at two seeding rates (60 and 90 lb/A) and Clearfield wheat was seeded at 60 lb/A. Due to dry conditions in the fall, wheat emergence was very poor and no jointed goatgrass emergence was observed in the fall. Much of the wheat and all of the jointed goatgrass emerged in spring 2002.

All Clearfield wheat plots were sprayed May 16, 2002, with tank mixture of imazamox + bromoxynil & MCPA at 0.04 + 1.0 lb ai/A to control jointed goatgrass, downy brome, and Russian thistle. The conventional wheat was sprayed with bromoxynil & MCPA only at 1.0 lb ai/A for Russian thistle control. Herbicides were applied with a tractor-mounted sprayer calibrated to deliver 10 gpa using 11001 flat fan nozzles. All plots were inspected visually for crop injury and weed control on May 29. Jointed goatgrass and Russian thistle control in the Clearfield wheat plots was 90 to 99%, while the downy brome control was marginal (~70%). In the conventional wheat, jointed goatgrass was not controlled while Russian thistle was effectively controllled 95%.

On June 25, wheat and jointed goatgrass populations were sampled in each plot. Populations were estimated by counting the number of jointed goatgrass plants, heads per plant, wheat plants, and wheat tillers per plant in four-10 by 6.6 foot areas evenly spaced apart in each plot.

Averaged over the four sampling areas within each plot, jointed goatgrass densities averaged 11, 18.3 plants/yd2 in the 60 and 90 lb/A conventional wheat seeding rates, respectively and 0.73 plants/yd2 in the Clearfield wheat.

Due to a harvesting error by the cooperator, grain yield was not obtained for the two conventional wheat seeding rates. The average yield of the two conventional seed rates was 68 bu/A compared to 32 bu/A in the Clearfield wheat.

 

        Jointed goatgrass        

                      Wheat                      

 

Plants

Heads

Plants

Tillers

Yield

Treatment

#/yd2

heads/plant

#/yd2

#/plant

bu/A

60 lb/A

11

2.8

26.1

4.2

68

90 lb/A

18.3

3.5

22.8

3.5

 

Clearfield

0.73

1.6

21.9

3.1

32

 

PUBLICATIONS: 

Evans, J.O. 2002. Current strategies to manage jointed goatgrass in winter wheat. Utah Ag. Exp. Stn. Producers Seminar. July 2, Blue Creek, UT.  110 attendees

 

Evans, J.O. 2002. Prospects for annual grass weed control in winter wheat using herbicide-resistant cultivars and altered crop rotation. Greenville Station Field Day. July 9. Logan, UT.  130 attendees.

 

TECHNOLOGY TRANSFER ACTIVITIES:  Results from this research were conveyed to producers at field demonstrations, and will be disseminated through articles in local and regional trade journals and popular press, Extension circulars, regional conferences, and updates to the World Wide Web Jointed Goatgrass home page.  Findings will also be published in appropriate professional journals.

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