National Jointed Goatgrass Research Program

 

New Proposal-2002

 

1. TITLE: Measuring Jointed Goatgrass Seed Viability Losses Across Environments

2. PRINCIPAL PERSONNEL: David W. Wilson and Stephen D. Miller, PO. Box 3354, Dept. of Plant Sciences, University of Wyoming, Laramie, WY 82071, Drew J. Lyons, 4502 Avenue I, Scottsbluff, NE and Gail A. Wicks, 461 West University Drive, University of Nebraska, North Platte, NE 69101 are the principle investigators. Co-operators include Wyoming and Nebraska wheat farmers.

3. TIME LINE: July 1, 2003 to June 30, 2005

4. HYPOTHESIS: Jointed goatgrass seeds lose viability more rapidly in no-till conditions than in conventional tillage systems

5. JUSTIFICATION: Jointed goatgrass seed longevity in the soil lasts five or more years (Donald 1991, Stump 1997, Wilson 2000). In a rotational experiment at North Platte, NE, jointed goatgrass left on the soil surface lost its viability with time. More seedlings emerge in the growing winter wheat when fall precipitation is less (Wicks, 2001). This proposal will establish plots in Nebraska and southeast Wyoming to measure jointed goatgrass seed viability losses over time, under variable moisture regimes, in standard wheat farming operations.  The study will use a new microchip and GPS seed tracking methodology, developed in the summer of 2001 and 2002, to relocate seed packets in tilled and untilled cropping systems for comparison of viability loss (Wilson, Wang and Miller, 2002). Basis of study is to show that tillage buries seed, therefore preserving viability.

6.  OBJECTIVES: To determine the affects of tillage vs no-till, burial depth, predation and moisture on the decline of jointed goatgrass seed viability in Wyoming and Nebraska wheat rotation systems. 

7. SUMMARY OF PROPOSAL: Jointed goatgrass emergence in the field is unpredictable, making it  difficult to manage with crop rotations, cultural, or tillage practices designed to decrease seed bank levels. After five years, jointed goatgrass emergence is quicker in plots where tillage has occurred. Potentially, seeds remaining on the soil surface may germinate and survive, germinate and die, or predators may remove the seeds. This study is designed to analyse how moisture conditions affect seed germination and if predation can cause seed losses.  Nylon mesh bags containing 50 joints will be placed on the soil surface and buried. These will be logged and relocated using GPS and microchip techniques. The seed packets will be placed in winter wheat fields, which may include a rotation with corn, sunflower, millet or bare fallow, before winter harvest, at six locations in Nebraska and Wyoming. These methods will allow the farmers’ normal tillage operations at each location, inclusive of minimal till, disc harrow, cultivator, rod weeder, etc,. compared to no-till checks. A scattered seed sub-study will be used to evaluate predation.  Precipitation and moisture data will be collected from each site to correlate precipitation with seed deterioration and viability losses. Initial viability and annual random samples will be removed in the spring and fall of each of the two subsequent analysis years.

8. METHODS & PROCEDURES: This study will use a methodology recently developed for the placement and retrieval of weed seed packets in tillage systems.  The new methodology uses 12mm microchips and allows for the tracking and retrieval of weed seed packets under tillage conditions with a GPS and microchip scanner. Sites will be established in various winter wheat rotation fields following harvest.  Flat, 200 micron nylon mesh packets, 5cm square, containing 50 locally obtained (NE) goatgrass joints (~100 seeds) and a 12mm microchip will be placed on the surface and buried at each of the following depths: 2.5cm, 7.5 cm and 15 cm at each location in a randomised directional compass cross pattern around a metal locator pin. All sites

will be logged with GPS and marked with the subsurface metal stake.  The packets will be relocated using the GPS data, a metal detector and the microchip transceiver.  Treatments (tilled vs untilled) with four replicates will be placed at six different sites (three experiment station and seven grower locations) in Wyoming and Nebraska. Experiment station sites at Archer, WY and North Platte and Sidney, NE will utilize onsite weather stations for moisture data (rings located beside weather station).  The untilled packets will be buried and relocated with a standard burial study template not requiring microchips. A laboratory sealed control will be retained in Laramie, Wyoming with a baseline viability test (before implantation) done in October of 2003. There will be four additional field analysis dates:  April 2004, October 2004, April 2005 and October 2005.  A sub-study of general surface predation will be conducted concurrently at the three experiment station locations.  Fifty goatgrass joints will be scattered on the surface, inside an imbedded 15cm deep by 30cm diameter plastic ring. Half of the scattered seed treatment rings will receive additional water treatments and both sets will be compared to matching field treatments at each site.  Moisture meters will be placed at all locations for monthly soil moisture readings, April through October to correlate moisture with seed decline. Germinated seedlings will be periodically removed from sites to prevent moisture loss.

9. EXPERIMENTAL DESIGN: The main study will use a randomized complete block design with four replications, and the sub-study will use a paired T-test (Hoshmand, 1993).

     Tilled Field Packets: 6 sites X 4 replicates X 4 sample dates over 2 years X 4 depths = 384 field samples

     No-till Checks: 6 sites X 4 replicates X 4 sample dates over 2 years X 4 depths = 384 field samples

     Loose Seed Surface Subplots: 3 sites X 4 replicates X 4 sample dates = 48 subplots

     Lab Stored Samples: 4 replicates X 5 sample dates = 20 laboratory samples

 

10. PUBLICATIONS: Results will be published as an extension bulletin, as well as in Weed Technology or Weed Science, with presentations at scientific meetings, and published as abstracts, proceedings or progress reports.

 

11. TECHNOLOGY TRANSFERS: Growers will be informed through meetings and the World Wide Web on ways jointed goatgrass seed viability declines and how best to manage the weed seed bank.

 

12. LITERATURE CITED:

Donald, W. W.  1991.  Seed Survival, Germination Ability, and Emergence of Jointed Goatgrass

     (Aegilops cylindrica) Weed Science; v39, p. 210-216

Hoshmand, A.R.  1993.  Experimental Research Design and Analysis: A Practical Approach for

     Agricultural and Natural Sciences.  CRC Press, Inc.,  Boca Raton, FL: 408pp

Stump, W.L.  1997.  The Ecology and Biology of Volunteer Rye, Jointed Goatgrass, and Downy Brome.

     PhD Dissertation, Colorado State University: 98pp

Wicks, G.  2001.  Personal communication of observations of current research study.

Wilson, D.W.  2000. Viability of Buried Weed Seed and Computerized Seed Detection Techniques.

     PhD Dissertation, University of Wyoming: 158pp 

Wilson, D.W., QQ Wang and S.D. Miller.  2002. Methodology for Tracking Weed Seed Drift and

     Viability in Tillage Systems.  2002 Annual Western Society of Weed Sci. Meetings, Salt Lake City, UT.

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