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Agricultural Research Center – Hays

Weed Science

The goal is to improve current or develop new safe and efficient weed management strategies in dry land cropping systems including ways to reduce risks of soil erosion and crop failure through plant residue and soil water management. Basic and applied studies in weed ecology, weed-crop competition, herbicide efficacy, environmental fate, crop tolerance, and cultural agronomics are conducted to assess the impact of weed interference, determine critical weed density thresholds, discover ways to optimize herbicide performance and crop safety, and integrate cultural and chemical control methods. Experimental and non-labeled herbicides are evaluated to assess their fit and potential usefulness in semi-arid dry land cropping systems.

Current Research Projects

Herbicide Resistant Weed Research

In 2007, graduate student Amar Godar confirmed the first cases of glyphosate resistance in kochia. By 2014, GR-kochia had spread throughout the Central and Northern Great Plains and into the Pacific Northwest. The mechanism of glyphosate resistance in kochia was found to be gene amplification (increased gene copy number) resulting in over-production of EPSPS enzyme, so that in the presence of glyphosate there is an abundant supply of uninhibited EPSPS. Subsequently, graduate student, David Brachtenbach, confirmed multiple resistance in kochia to glyphosate and dicamba herbicides. Furthermore, in collaboration with Drs. Mithila Jugulam and Vijay Varanasi a single Kochia population was found with resistance to four modes of action. Multiple statewide field trials demonstrated that applying various soil active herbicides prior to kochia emergence were usually much more effective in managing kochia than most postemergence-applied herbicides. The findings of this research have been widely adopted by growers for improved management of kochia.


From 2012 until retirement Phil documented the distribution of glyphosate-resistant Palmer amaranth in Kansas and determined in greenhouse trials that numerous populations have evolved resistance to as many as five herbicide modes of action. In his final act of employment, he accepted invitations to chair the organization of one of seven regional herbicide resistance listening sessions jointly sponsored by the US Department of Agriculture – Animal and Plant Health Inspection Service, the United Soybean Board, and the Weed Science Society of America to identify new ideas and approaches to stem the evolution and spread of herbicide resistant weeds. More than 100 diverse stakeholders from six Great Plains states (CO, KS, MT, OK, NE and WY) attended and provided input. Also, he attended and represented the Weed Science Society of America at the Listening Session held in the Pacific Northwest.   

Corn Research

Corn herbicide research at the station is devoted to development of new and maintenance of existing herbicide technology in dryland and limited-irrigation production systems. New technologies, such as herbicide-resistant hybrids (Roundup-Ready®, Liberty-Link®, and Clearfield®) as well as new herbicides such as Balance Pro®, Callisto®, and Option®, are evaluated for weed control efficacy and crop response. These new technologies are compared with existing herbicide programs to determine strengths and weakness on weeds common in the western Great Plains. Specific weed problems, such as kochia, Palmer amaranth, and longspine sandbur, are evaluated for competitiveness with the crop and to determine which management practices best control these weeds. All of these areas of research are integrated to determine the weed management programs that are most cost effective for the producers of our area.

A study was initiated in cooperation with Dr. Anita Dille, Weed Ecologist in Manhattan, to evaluate Palmer amaranth growth and interference in corn.  Crop biomass and plant height was measured for both the crop and weed to evaluate the growth rate of each during the growing season.  The crop and Palmer amaranth was grown in monoculture and together to evaluate the effects of not only the effect of weeds on corn, but also to see what competitive effect the crop can have on weeds.

A study was initiated in cooperation with Dr. Dille to evaluate the effects of variable rate technology in a large production field situation.  With the assistance of Dave Braun, ARCH Farm Manager, and Spencer Casey, ARCH Administrative Assistant and GPS Technician, the group was able to apply herbicide at different rates with a specially equipped sprayer.  Locations where rates changed were mapped using GPS.

Grain Sorghum Research

Grain sorghum (milo) herbicide research under the direction of Dr. Phil Stahlman is devoted to the development of new and maintenance of existing weed management programs in the western Great Plains. New herbicide technologies such as Paramount®, Aim®, and Starane® are compared to existing herbicides to determine weed control efficacy and crop response. These comparisons are made under various management systems to determine the most economical weed control programs for local producers.

Mark Lubbers, graduate student, worked on the development of fluroxypyr in grain sorghum during 2001-02.  Mark has evaluated the effects of herbicide application timing, crop response, tank mix partners, and adjuvant effects on fluroxypyr activity in grain sorghum.

Since grain sorghum is a popular crop in Western Kansas, research will continue on weed control programs as well as other biological aspects of sorghum production.

Grain sorghum (milo) herbicide research under the direction of Dr. Phil Stahlman is devoted to the development of new and maintenance of existing weed management programs in the western Great Plains. New herbicide technologies such as Huskie(R), Lumax/Lexar(R), and Starane(R) are compared to existing herbicides to determine weed control efficacy and crop response. These comparisons are made under various management systems to determine the most economical weed control programs for local producers.

Mark Lubbers, graduate student, worked on the development of fluroxypyr in grain sorghum during 2001-02.  Mark has evaluated the effects of herbicide application timing, crop response, tank mix partners, and adjuvant effects on fluroxypyr activity in grain sorghum.

Dr Stahlman led a statewide research effort that convinced Syngenta Crop Protection to register Lumax/Lexar(R) for use in grain sorghum. These herbicides were subsequently registered for the same use in other sorghum producing states.  Since grain sorghum is a popular crop in Western Kansas, we are continuing to investigate other registered herbicide that could potentially be used in grain sorghum.

Soybean Research

Typically soybean production in Western Kansas is not popular because of the lack of rainfall.  Dryland soybeans usually suffer from the combination of heat and drought and are not as profitable as other more tolerant crops.

Despite these downfalls, research on soybeans continues.  The ARCH Weed Science group has a study evaluating the environmental effects of using Roundup technology.  This study includes using Roundup Ready soybeans in the cropping system and is scheduled to be completed in a few years.

Sunflower Research

Sunflower production in Kansas is growing and so is sunflower research conducted by the ARCH Weed Science group. 

Weed control in sunflower is a challenge.  Grass control is typically not too difficult due to the availability of several graminicides (grass herbicides).  Broadleaf weeds, on the other hand, are quite a challenge.  Most herbicides that control common broadleaf weeds found in sunflowers also control the crop itself!  Therefore, many studies are geared towards evaluating crop tolerance and weed control for various herbicide combinations.

A great deal of effort has been focused on evaluating the crop tolerance and weed control effects of sulfentrazone.  Past studies have shown excellent crop safety and weed efficacy when applied at the correct time.  Continued research is being conducted on this herbicide and possible tankmix partners.

Other research in sunflower includes the use of Clearfield sunflower.  This new technology would couple herbicide resistant sunflower varieties with Beyond herbicide to provide weed control.  Dr. Stahlman has conducted numerous studies on this technology and is currently evaluating the performance of different varieties.  More information on Clearfield sunflower will be available soon.

Wheat Research

Wheat research with the ARCH Weed Science group is king!  Along with several long-term jointed goatgrass projects in wheat and recropping studies, the group conducts countless herbicide performance trials each season.

Herbicide performance trials include old and new herbicide technology and how each perform in a weed control program in wheat.  The first publications of Maverick Pro and Olympus in wheat were written by Pat Geier and Phil Stahlman from work conducted at the Agricultural Research Center - Hays. 

The recent introduction of Clearfield winter wheat in the central Great Plains has established the importance of ongoing research on this technology.  Currently, several studies containing Clearfield wheat are being conducted on station and at outlying locations.  Trials include the effects of proper application timing for weed control of many broadleaf weeds and winter annual grasses.  Much attention is being put on the proper timing for feral rye control and the most appropriate adjuvant selection for maximum weed control and minimal crop injury.

Wheat research at the Ag Research Center will continue to expand as more advanced technology becomes available. 

Recropping Studies

Managing winter wheat can be a challenge in Western Kansas.  Some years drought or other natural phenomenon occur that destroys a wheat crop.  The remedy for this is either to replant wheat or revert to a summer crop.

Recent studies conducted by the Weed Science group at the Ag Research Center in Hays has evaluated the effects of recropping to crops such as soybean, corn, grain sorghum, forage sorghum, and alfalfa after varying application rates of Maverick Pro or Olympus herbicides.  These studies are essential in determining the minimum time required to allow planting a summer crop after a failed wheat crop.

In 1994, Phil collaborated with weed scientist in CO, NE & WY to establish long-term field studies in each of the four states to assess the benefits and risks of using only glyphosate (Roundup®) multiple times annually for weed control in Roundup Ready® crop compared to more diverse herbicide programs in continuous corn versus corn grown in rotation with other Roundup Ready® crops. During the first five years, multiple annual applications of only glyphosate proved the most efficacious and economical weed management program regardless of crop rotation, but continued repeated use of a lower-than-recommended rate of glyphosate changed the composition of the weed population to weed species with greater tolerance to glyphosate and to species with wide germination patterns allowing some plants to escape glyphosate compared to species with narrow germination patterns. In the Kansas trial, 12 years of exclusive glyphosate use multiple times annually selected for glyphosate-resistant kochia. The research confirmed the risks associated with repeated use of glyphosate only and the longer term benefits of diverse herbicide use programs for herbicide resistance management. 

Biology Research

Although research on herbicide performance is important, it is not the only thing involved in Weed Science.  Researchers need to know the fundamentals on how crops grow, what they require for proper growth, how they interact with weeds in the field and how cultural practices influence the way crops function.

Dr. Phil Stahlman has put together a strong research program on crop-weed interference, weed thresholds, and the effects of cultural practices in various cropping systems.  We currently have several studies looking as various aspects of weed biology in multiple cropping systems.

Our crop rotation study was established to evaluate the effects of crop rotation in a dryland environment.  Specific crop rotations were established to evaluate the effects of yield due only to a rotation component.

A study looking at the ecological benefits of Roundup Ready cropping systems was established to evaluate what effects the use of Roundup technology has on the environment.  Soil infiltration, insect, nematode, and other valuable data is being collected to evaluate if benefits are seen with Roundup systems over conventional cropping systems.  This study was conducted in cooperation with Dr. Kassim Al-Khatib, former KSU Weed Scientist in Manhattan.

Jointed Goatgrass

The Weed Science group at the KSU Ag Research Center-Hays was heavily involved in jointed goatgrass research. They conducted three long-term experiments.  Projects are funded by the National Jointed Goatgrass Research Program, Kansas Wheat Commission and BASF.  Dr. Stahlman was instrumental in securing long term federal funding to create the National Jointed Goatgrass Research Initiative.

  • "Controlling Jointed Goatgrass in Winter Wheat Rotations Using Cultural Practices"

    This study, located at the KSU Ag Research Center in Hays, was initiated in the fall of 1996.  The study was based on the hypothesis that integrating winter wheat cultivars, limited tillage during fallow periods as compared to no tillage, and multi-year crop rotations will hasten control and reduce the impact of jointed goatgrass more than any of the component practices alone.

    What we learned was that wheat cultivar and fallow weed management systems have very little effect on jointed goatgrass populations.  However, a three or four year crop rotation reduced populations 10 to 30% compared to a wheat-fallow rotation.  Grain sorghum yield was higher in 4 of 5 years when grown in the GS-F-W compared to the GS-SF-F-W rotation.  Inadequate soil moisture or depleted soil minerals may be the result of adding sunflower into the rotation. 

  • "Clearfield Winter Wheat Risk Assessment"

    The risk assessment study, located at the Sandyland Research Center in St. John, KS, was established in August 2001.  The study was based on the hypothesis that the prolonged use of Clearfield winter wheat would increase the risk of transferring herbicide resistance to jointed goatgrass and hasten selection of herbicide resistant biotypes in other winter annual grass weed species.

    The first wheat crop was seeded in October 2001 and the jointed goatgrass population, averaging only 2 to 5 plants/square meter, were determined in late November.  Low populations in the fall and carrying on through harvest were believed to be related to extremely low moisture.

  •  "Prolonging Clearfield Technology with Certified Seed and Crop Rotation"

    This study, located at the KSU Ag Research Center in Hays, was initiated in the fall of 2001.  The study was based on the hypothesis that using certified versus bin-run Clearfield wheat and restricting the use of Clearfield technology in any given field to not more than once every other year.  More frequent use will limit development of resistant weed biotypes and prolong the utility of Clearfield technology for the management of jointed goatgrass.

    Although conditions were dry during the early part of the 2002-03 wheat growing season, the wheat yields were well above average and jointed goatgrass was able to grow and set seed.  As expected, JGG counts indicated major differences between plots sprayed with Beyond (Clearfield) and those sprayed with Rave.

 

 

 

Contact Information

 

 

 

Vipan Kumar 
Weed Scientist
KSU Ag Research Center
1232 240th Avenue
Hays, Kansas 67601-9228
(P) 785-625-3425 x214
(F) 785-623-4369
Email: vkumar@ksu.edu

Retirement

 

Feb 07, 2017 - After 42 years of service to Kansas State University, the profession of Weed Science, and agricultural producers across the globe, Dr. Phil Stahlman has announced his retirement.  A reception was held on March 3rd, 2017 in honor of Phil Stahlman's career accomplishments.

Recognition

 

In 2012, Phillip W. Stahlman honored with Weed Science Society of America Fellow Award (PDF)

The Weed Science Society of America (WSSA) honored more than two dozen individuals for their outstanding contributions to the field of weed science. The awards were presented during the organization’s annual meeting, held this year in Waikoloa, Hawaii.  The organization presented Phillip Stahlman with its highest recognition of Fellow.  Read more...

 

In 2017, Dr. Stahlman was presented with Presidential Award of Merit from the Western Society of Weed Science (WSWS).

 

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