Sheep integration for diverse and resilient organic cotton systems

Progress report for LS22-375

Project Type: Research and Education
Funds awarded in 2022: $370,998.00
Projected End Date: 03/31/2025
Grant Recipients: Texas A&M AgriLife Extension; Angelo State University; Texas Tech University; Texas A&M University
Region: Southern
State: Texas
Principal Investigator:
Dr. Reagan Noland
Texas A&M AgriLife Extension
Dr. Justin Benavidez
Texas A&M AgriLife Extension Service
Dr. Caitlyn Cooper-Norris
Texas Tech University
Dr. Holli Leggette
Texas A&M University
Dr. Reid Redden
Texas A&M AgriLife Extension
Dr. Cody Scott
Angelo State University
Bob Whitney
Texas A&M AgriLife Extension
Expand All

Project Information


The economic opportunity represented by organic cotton premiums has captured the interest and commitment of many producers across the South. Semi-arid West Texas is conducive to successful organic cotton production due to generally lower pest and disease pressure (and reduced reliance on pesticides) compared to much of the Cotton Belt. However, mechanical- and hand-weed control are not environmentally nor economically sustainable. Due to limited water, portions of irrigated land are left fallow and rotated annually. During fallow periods, this acreage is plowed several times to suppress weeds. Sheep integration in organic cotton systems has potential to suppress weeds, reduce tillage, and add value to the overall system. Furthermore, conversion of dry acreages to perennial forage crops would be more environmentally sustainable than the current regime, and would supplement sheep grazing opportunities. A new system, integrating sheep, cotton, annual forages, and perennial forages poses unique potential for diversification and ecological resilience. The proposed research seeks to identify optimum practices for “sheep-weeding” in organic cotton (i.e. cotton growth stage, sheep stocking rate and duration). The work will also assess establishment methods and species for conversion of degraded cropland to perennial forages. System impact will not be based on single response variables, but a network of components characteristic of the whole system. This comprehensive set of field research trials will be coupled with dynamic economic analyses to explore critical questions and inform educational products for the public. An advisory council of stakeholders will guide efforts and help interpret and leverage findings and future work.

Project Objectives:

Objective 1. Employ Neef and Neubert’s six dimensions of participatory research framework to facilitate positive, favorable interaction between researchers and stakeholders and enhance the viability and livelihood of organic cotton stakeholders in the South.

a. Coordinate needs assessment via Q-methodology to explore stakeholder perspectives, needs, and expected benefits and outcomes of the proposed project. 

b. Establish a project advisory board

c. Host regular town-hall meetings to convene with stakeholder groups on research progress and direction. 

Objective 2. Assess agronomic and stocking management implications of sheep-weeding in cotton

a. Year 1: Evaluate timing of sheep-weeding initiation relative to cotton growth stage, and sheep-weeding termination relative to varying thresholds of weed herbage mass removal. 

b. Years 2 and 3: Compare optimized sheep weeding strategy (from Obj. 2a) to alternative and otherwise standard weed management systems. 

Objective 3. Identify best-suited perennial and annual forage management options for converted land

a. Test establishment success, forage yield and nutritive value, and soil health indicators across a range of forb inclusion rates with native perennial grasses.

b. Assess forage yield, nutritive value, and sheep grazing preference among summer and winter annual legumes and legume-grass mixtures. 

Objective 4. Develop, deliver, and test public resources, economic decision support tools, and stakeholder resources for continued education and assessment of sheep-weeding practices.

a. Economic enterprise budgets informed by measurements in Objectives 2 and 3. 

b. Develop and deploy reusable learning modules

c. Publish findings in popular press articles and develop educational videos


Click linked name(s) to expand/collapse or show everyone's info


Materials and methods:

Year 1 Field Research Trials

Sheep-weeding in Cotton - This experiment was conducted in San Angelo, Texas during the 2022 cotton season at the Angelo State University Management, Instruction, and Research (MIR) center. A travelling irrigator was used persistently in response to the abnormally hot and dry 2022 growing season, but both crop and weed growth were limited by the environmental conditions. Portable electrified net wire fencing was used to separate plots and contain sheep during grazing events.  Electric net fencing also served as a barrier to help keep deer pressure down in the plots. An The trial was designed as a 3x3 factorial with treatments including three different cotton growth stages to initiate grazing (4-leaf, 8-leaf, and mid-bloom) and three different levels of grazing intensity (approximately 70%, 90%, and 100% weed removal with presumably greater cotton damage with increasing intensity). Differences were identified using α = 0.1.   Each replication also included a weedy-check and weed-free check. To maintain our weed free check (WFC), chemical control was used at the beginning of the season and then manually weeded throughout the season. Our weedy check (WC) had no control.  The trial was arranged in a randomized complete block design with four replications. Before and after each grazing initiation, aerial imagery was collected with a UAV. This allowed quantifying weed biomass removal by sheep by analyzing weed canopy cover percentage before grazing and removal after grazing. Quadrat imagery and clippings were collected (three 0.67 m2 quadrats per plot) as another way to quantify weed biomass removal. During each grazing treatment, notes were taken every five minutes on the number of sheep grazing weeds, grazing cotton, and how many were idle in the plot. These numbers were converted to Sheep Grazing Minutes (SGM) to determine, in scalable units, a level of grazing intensity required to accomplish the same amount weed removal. In the first and second initiation timings, sheep were grazed in the plots two or one more time during the season for plot maintenance. To measure final cotton and weed biomass, all cotton plants were harvested from a 3-m length of two center rows per plot, and weed biomass was harvested from the same area, including the interrow space. Biomass was weighed fresh then subsampled (approx. 500 g) for dry matter determination. 

Perennial forage trials were planted at San Angelo and Lubbock, TX in spring 2023. Plots are 5 × 20 ft and treatments (forb inclusion rates = 0, 20, 40, and 60% pure live seed) were planted in a randomized complete block design with 4 replications. Sites have received some precipitation since planting, but have not yet established. 

Summer annual forage trials were planted at one site last year and withheld at other sites due to the drought. The planted site failed. Winter annual forage trials were planted at two sites across West Central Texas, comparing forage yield of winter legumes in combination with triticale and turnips. Trials were successfully established. Forage biomass has been sampled and is currently being processed. 

All other project objectives will be initiated in 2023. 


Research results and discussion:

The 2022 growing season was extremely hot and dry in West Texas. San Angelo experienced the hottest July on record (in 116 years), with an average daily high of 103.5 F and average temperature of 89.7 F. The area received only 3.37 inches of rain from January through July (71% below average for this period). Due to these conditions, all summer annual forage trials failed (as all sites were non-irrigated). The sheep-in-cotton trial was irrigated as frequently as possible throughout the season, enabling enough plant growth for crop and weed measurements, but water was inadequate for harvestable cotton production. 

In the first year of the sheep-weeding trial, grazing intensity had the greatest effect on total weed biomass (p = 0.036), weed canopy (p = 0.024), and the cotton to weed ratio (p = 0.074). The most intense grazing treatment (target 100% removal) at the 8-leaf initiation resulted in 89% and 49% greater weed biomass reduction than the least and moderately intense treatments, respectively. Similarly, the most intense grazing treatment at the mid-bloom initiation reduced weed canopy cover 33% and 80% more than the least and moderate intense grazing, respectively. Final weed biomass was less due to 8-leaf initiation with 100% weed removal (21 kg ha-1) than mid-bloom initiation with 100% weed removal (77 kg ha-1), 4-leaf initiation with 100% removal (180 kg ha-1), as well as the weedy check (244kg ha-1) (Figure 1). Grazing initiation time had the greatest effect on total amount of sheep grazing minutes required for each plot (p < 0.0001). To achieve the same weed biomass removal as the 4-leaf grazing initiation, 8-leaf and mid-bloom initiations required 46% and 135% more sheep grazing minutes, respectively. As sheep were introduced into each plot, they all were not eating at the same time and/or throughout the entire time in the plot. The SGM unit allows for a more quantifiable metric to determine how long sheep should be grazing in the plot, rather than time (e.g., 30 minutes, 1 hour). Weed management treatments did not influence cotton canopy or final cotton biomass, likely due to a season of severe drought. Timing (cotton growth stage) of grazing initiation also did not influence cotton canopy, cotton biomass, weed biomass, and weed canopy to the same effect as grazing duration.

Treatment Effects on Weed Biomass
Sheep-weeding effect on ultimate weed biomass at the end of the season.
Sheep grazing effect on weed coverage
Weed canopy coverage before and after grazing at each time and intensity

Findings from this first year of research show potential for sheep herbivory to be applied in cotton systems for weed control. In addition to a more integrated weed management system, farmers may also develop a new revenue stream by raising the sheep and selling them to market. This may also be important for organic producers that generally have smaller operations and are looking to diversify their income and production. More research is needed to identify optimum management options and quantify economic and production differences between sheep weeding and other weed management systems.

Participation Summary


Educational approach:

Educational goals/deliverables include the development and dissemination of two reusable learning modules, six Extension and popular press articles, and two educational videos. Further, graduate student education is underway with two graduate research assistants on the project. 

Year 1 Progress:

M.S. student Matthew Stewart began his assistantship on this project in May 2022 and coordinated the first year of field research trials integrating sheep into cotton systems. He has completed his first year of coursework, and will conduct his second year of field-research in 2023. Matthew shared research findings from his first year in an oral presentation at the American Society of Agronomy Meetings (Baltimore, MD), and as a research poster at the Texas Plant Protection Conference (Bryan, TX), and the Beltwide Cotton Conferences (New Orleans, LA). He placed 2nd in the graduate student poster competition at Texas Plant Protection, and 3rd in the Sustainability Conference at Beltwide. 

M.S. student Nathaniel Jackson began an assistantship on this project in Spring semester 2023. He will be working with Dr. Holli Leggette on the participatory research, communication, and outreach components of the project. 

Stakeholder education products and events are being planned and coordinated for the 2023 field season. 


Educational & Outreach Activities

1 Consultations
1 On-farm demonstrations
1 Published press articles, newsletters
3 Webinars / talks / presentations

Participation Summary:

Education/outreach description:

Year 1 progress:

One direct consultation was made with a producer who had integrated similar practices previously and was considering options to continue using sheep on his organic cotton farm. The project team also coordinated with 2 key producers to host RFD-TV America's Heartland film crew who featured SARE with a special feature (reported as an on-farm demonstration). This feature can be viewed here (beginning at 12 minutes 30 seconds): . The communications team from Angelo State University (collaborating institution) also featured our work in their January 2023 magazine "Fiat Lux" and on their Agriculture Department's website: Town-hall meetings and field tours are being coordinated in 2023. 

Project Outcomes

Project outcomes:

The first year of this project was dedicated to establishing field research trials and building relationships with collaborators and stakeholder groups. This project outcomes will begin in Year 2 and be most evident in the final year of the project. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.