1a.Objectives (from AD-416):
Compare factors within and among modern cropping systems that may impact soil microbial communities, plant-microbe interactions, and plant health and productivity.
1b.Approach (from AD-416):
To assess the weed management legacy on subsequent crops, several agricultural parameters will be measured in glyphosate resistant (GR) and non-GR sweet corn isolines, grown in fields with a legacy of glyphosate use and in fields where glyphosate has not been used for the past three or more years. The field design will allow comparisons of the plant genotype in isolation from the legacy of the farming system management and the plant genotype by systems interactions. Plots will be 15’ wide by 30’ long. For treatments receiving glyphosate, the herbicide will be applied at 0.84 kg a.e. ha-1 in a 130 Lha-1 spray volume at a pressure of 138 kPa when soybean and maize are at the V4–V5 and V5–V6 growth stages, respectively. Plots not receiving glyphosate will be hand-weeded periodically during the growing season. In addition, a subsample of GR and non-GR isolines of sweet corn plants plots will be challenged or not challenged with Goss’s wilt (Clavibacter michiganensis subsp. nebraskensis). Soil and plant samples will be taken at different times throughout the growing season, and shipped to Beltsville, MD for nutrient and microbial analysis.
Field sites for this research have been identified and prepared for the trials. One site has a history of glyphosate use, which required little preparation. However, the other site has been in sod for over 10 years and has not had a glyphosate application during that time. The site with sod required multiple mechanical cultivations in order to kill the sod without the use of glyphosate. Sweet corn seed has been secured via a material transfer agreement. Near iso-genic lines will be used; one line with the glyphosate-resistant trait as well as the non-transgenic isoline. A source of Goss's wilt inoculum has been procured and detailed plans for inoculation have been developed. A preliminary trial indicated successful inoculation and pathogen development on sweet corn lines that will be used in this work.