Mitigation of Potential Adverse Effects of Transgenic Crop Production for Long-Term Improvement of Soil Health

View the project final report

Commodities

• Agronomic: corn, soybeans

Practices

• Crop Production: cropping systems, tissue analysis
• Natural Resources/Environment: biodiversity, soil stabilization
• Soil Management: organic matter, soil analysis, soil chemistry, soil microbiology, soil quality/health

Crop production in Iowa is dominated by short rotations of GM corn and soybean relying on glyphosate (active ingredient of Roundup). Despite claims that glyphosate rapidly dissipates and becomes immobilized in the environment, recent studies report that over 1000 ppb of residues of glyphosate and its decomposition products, were detected in soils under intensive glyphosate use. Based on reports that glyphosate residues affect soil biology coupled with poor weed management due to glyphosate-resistant weeds, many farmers are considering a change toward non-GM cropping systems. However, little information is available on time required for dissipation of glyphosate/AMPA residues or for soil health buildup to guide farmers in assessing the sustainability of management during transition from GM to non-GM crops. We will monitor glyphosate soil residues and soil health indicators during transition to establish baselines for improvement of soil using ecologically sound soil and crop management, which will decrease contamination of surface water with glyphosate in runoff and improve soil biology. Transition may improve profitability as premiums are paid for non-GM grains. Decreasing or eliminating use of glyphosate promotes socially responsible benefits by minimizing exposure of the rural community to drifts of glyphosate spray and providing healthy ecosystems through improved soil health.

1. Set up a glyphosate/AMPA monitoring protocol for residues in soils using an intensive soil sampling approach at sites prone to glyphosate drift or runoff and at sites not exposed to glyphosate.
2. Concurrently monitor soil health by measuring selected indicators in crop management transition fields without glyphosate. Crop performance (tissue nutrient contents, N response and leaf chlorophyll, and grain yield) will also be measured and related to soil health status.
3. Develop a guide for farmers to track soil health improvement after transition from GM cropping.