Final report for GNC23-382
Project Information
Dryland agriculture is critical in the High Plains but is often subject to water scarcity, weed pressure, and soil health degradation. One way to improve water storage, weed control, and soil health is by increasing the amount of crop residue left on the soil surface. Winter wheat is a major dryland crop in the High Plains, and its residue has the potential to contribute significantly to these goals. However, the extent to which winter wheat residue is affected by wheat stem sawfly (WSS) and its relation to water storage, soil health, and subsequent crop yield is not fully understood.
The goal of this project is to investigate the relationship between infested and non-infested winter wheat residue, water storage, soil health, and following crop yield in a dryland cropping system. The project aims to (1) quantify the rate and extent of infested and non-infested residue degradation over time, (2) evaluate the impact of infested and non-infested wheat residue on soil-water storage and following corn yield, (3) assess the effects of infested and non-infested residue degradation on soil health indicators, and (4) compare the residue quality of commercially available wheat varieties that differ in their stem thickness.
These experiments will be conducted at the University of Nebraska High Plains Agricultural Laboratory (HPAL) over several years (2021-2025), where some of the highest levels of WSS infestation have been observed. To measure residue degradation, composited samples of infested and un-infested wheat tissue of twelve varieties will be placed on a bare soil surface within enclosures, and the remaining residue amounts will be monitored over time. Standing and lodged residue on large plots will also be monitored until corn harvest the following year. Access tubes for use with an Am-Be neutron gauge will be used to measure soil water content at various intervals over time, and soil samples will be collected to monitor nutrient cycling and soil health.
The experiments will provide insights into the relationship between WSS infestation and winter wheat residue degradation, soil-water storage, following corn yield, and soil health in a dryland cropping system. The findings are relevant to farmers in the region who are battling WSS infestation and seeking to improve soil health and crop productivity and profitability.
This proposal outlines a robust, multi-year study that has the potential to provide valuable information to the agricultural community in order to sustainably maintain dryland winter wheat production in regions impacted by WSS.
Farmers in the High Plains region will be able to (1) improve water storage and soil health by understanding and increasing winter wheat residue on the soil surface and their relationship with the major wheat pest WSS, and (2) identify the effects of WSS infestation on water storage, soil health, and subsequent crop yield. This will lead to more efficient and sustainable dryland cropping system practices, resulting in increased crop productivity and environmental benefits. Major outcomes will be shifts in the way residue is managed under WSS infestation to promote ecological benefits that translate to economic viability. Specifically, these outcomes may influence wheat variety selection, protection of residue through agronomic practices related to no-till product, and improved monitoring of residue and soil health and soil water storage. We will evaluate the success of our research and outreach endeavors by formal surveying, continued engagement with targeted farmers for feedback, and the use of resources generated by the project. Long-term outcomes could include increased or sustained wheat acreage, improved corn and subsequent crop yields as measured by local reporting and insurance claims, as well as continued engagement of growers in research efforts at the High Plains Agricultural Lab.
Research
Experimental Design
Split-plot RCBD with three different winter wheat varieties was selected to evaluate biomass decomposition rates, soil moisture retention, and corn yield.
Residue Biomass samples were collected at two-month intervals from wheat harvest to subsequent corn harvest.
Volumetric Water Content Measurement: VWC was measured using a 503TDR Hydroprobe from wheat harvest until the following corn harvest.
Corn Yield Measurement: A 20-foot section from the two central rows of each plot was harvested, corresponding to the locations of water content measurements.
Enclosure Study: RCBD with twelve wheat varieties (both WSS-infested and uninfested) residue were weighed and placed on the soil surface within a wood box enclosure with wire mesh on the top and bottom designed to prevent residue loss while allowing sunlight, air, and water penetration to simulate natural decomposition.
Residue Persistence, Soil Water, and Crop Rotation Effects
Wheat residue persistence declined over time as expected, but was not significantly affected by wheat stem characteristics or sawfly infestation. Residue decomposition rates were similar across varieties and infestation categories (infested and uninfested stems). Soil volumetric water content was not influenced by stem type or sawfly injury, and dryland corn yield following wheat was unaffected by residue characteristics or sawfly infestation. These results suggest that, under the conditions evaluated, wheat stem sawfly does not substantially alter the soil water conservation benefits of wheat residue in no-till dryland systems.
Table 1. Grain yield of dryland corn planted on wheat stubble of three winter wheat varieties with different types of stem solidness traits in 2023 and 2024 at the High Plains Agricultural Laboratory, Sidney, NE.
|
Wheat Variety |
Exclusion Cage |
Yield |
|||
|
2023 |
2024 |
||||
|
kg ha-1 |
SE |
kg ha-1 |
SE |
||
|
Robidoux |
Uninfested |
7493 |
715 |
3969 |
455 |
|
Robidoux |
Infested |
8078 |
715 |
4244 |
455 |
|
Fortify SF |
Uninfested |
7117 |
715 |
3689 |
455 |
|
Fortify SF |
Infested |
7191 |
715 |
4055 |
455 |
|
Spur |
Uninfested |
7552 |
715 |
3588 |
455 |
|
Spur |
Infested |
8115 |
715 |
3672 |
455 |
Note. There were no statistical differences at the α = .05 level using estimated marginal means.
Implications for Sustainable Cropping Systems
Although thicker and stronger stems improve standability, harvestability, and reduce lodging risk, biological control via parasitoids was the most consistent mechanism for reducing yield losses associated with wheat stem sawfly.
Educational & Outreach Activities
Participation summary:
With this project, we were able to reach various educational activities such as consultations, on-farm demonstrations, and tours In terms of formal educational content, the team has created 2 factsheets and presented the information on them to farmers at 2 field days so far. Additionally, the team has presented this data at 3 different symposiums. Outreach efforts are ongoing with continuous updates, and there are plans for more presentations and educational materials to come. However, there have been no online trainings, journal articles, or published press articles yet.
Project Outcomes
Contribution to Agricultural Sustainability
Our project has advanced agricultural sustainability in multiple dimensions—economic, environmental, and social—by addressing wheat stem sawfly (WSS) management in dryland wheat systems.
Economic Benefits
- Cost-Effective Management: Unlike chemical controls, which are largely ineffective against WSS, promoting parasitoid survival requires no additional inputs or specialized equipment. Farmers can leverage existing practices such as residue retention and reduced tillage, lowering costs and improving profitability.
- Stable Crop Rotation Yields: Corn yields following wheat were unaffected by WSS infestation or stem type, ensuring rotational stability and predictable income streams.
Environmental Benefits
- Enhanced Soil Health and Water Conservation: Retaining wheat residue and minimizing tillage—practices that also favor parasitoid survival—reduce erosion, improve soil structure, and enhance precipitation storage efficiency.
- Climate Resilience: Stronger stems improve standability and residue persistence, which supports soil moisture retention under variable precipitation patterns.
Social Benefits
- Knowledge Transfer and Adoption: Through 3 field days, 4 conference presentations, and Extension outreach, we reached over 450 producers, breeders, and industry stakeholders, equipping them with science-based strategies for integrated pest management.
- Community-Level Impact: Adoption of biologically based WSS management fosters collaboration among farmers and researchers, promoting sustainable practices that benefit entire production regions.
- Long-Term Resilience: By reducing reliance on chemical controls and improving soil health, these strategies contribute to food security and rural economic stability.
Future Sustainability Contributions This project lays the foundation for scalable biological control of WSS. Ongoing research will:
- Identify landscape factors that enhance parasitoid persistence.
- Develop predictive models for biological control effectiveness under climate variability.
- Provide practical guidelines for farmers to integrate natural enemies into cropping systems.
By aligning pest management with soil and water conservation practices already common in dryland systems, this approach ensures sustainability without imposing additional burdens on producers.
Since we did not observe significant effects of wheat residue type or infestation level on soil water, we learned that farmers should focus more on the parasitoid that feeds on the wheat stem sawfly to increase yields and maintain standing wheat stubble. Going forward, we will work to develop biological control into a predictable and scalable management tool for producers. By identifying conditions that promote parasitoid establishment, future Extension efforts will focus on providing growers with clear, practical guidance on how to manage fields in ways that attract, sustain, and benefit from these beneficial insects.
Importantly, this approach shifts wheat stem sawfly management from reactive control toward a preventive one. Producers can reduce yield losses, maintain residue benefits critical for soil water conservation, and avoid reliance on ineffective chemical controls.
Overall, this project catalyzed a broader research and Extension framework aimed at helping producers bring effective biological control onto their land, increasing resilience of dryland wheat systems.