Data collected included:
Cereal rye and weed biomass at the time of cover crop termination, soil moisture at planting, weekly Palmer amaranth emergence counts, Palmer amaranth control throughout the growing season, soybean canopy closure, Palmer amaranth density in low and high management plots, Palmer amaranth biomass in no management plots, along with soybean harvest population counts and yield

Results (Years 1&2):
• Cereal rye produced 1070 lb A-1 in 2015 and 1950 lb A-1 in 2016 of dry biomass at the time of cover crop termination.
• Cereal rye was not effectively controlled by mowing in either year and produced another 1140 lb A-1 one week later in 2015 and 517 lb A-1of dry biomass two weeks later in 2016 that was then terminated with glyphosate.
• At the time of cover crop termination, winter annual and early summer annual weed biomass was 77% and 84%, respectively, lower in the cereal rye plots compared with the no cover controls.
• There was no significant difference in soil moisture between the plots at the time of soybean planting in 2015; however, in 2016 soil moisture was higher with a cover crop compared to no cover at a 3 and 4.7-inch soil depth.
• Palmer amaranth emergence started on June 16th in 2015 and June 7th in 2016 with continued emergence well into August, with peak emergence occurring in the middle to end of June.
• Adequate precipitation after Valor was applied PRE resulted in good control of Palmer amaranth in the low and high management systems in 2015; however, warm temperatures and a lack of precipitation early in the season in 2016 resulted in earlier POST applications to control emerged seedlings.
• The POST Liberty applications effectively controlled emerged Palmer amaranth. The addition of Warrant to Liberty suppressed some of the new Palmer amaranth emergence in 2015 and 2016 compared with Liberty alone. However, a late POST application of Liberty was needed in 2016 in the high management plots due to late rainfall events that triggered new emergence of Palmer amaranth.
• Canopy closure occurred earlier in the 7.5-inch row widths in both years, with over 80% canopy cover occurring 2 to 4 weeks earlier in narrow rows compared with 30-inch rows. Soybean canopy cover was not affected by the rye cover crop or cover crop termination method.
• The later canopy closure in the 30-inch rows prolonged the emergence of Palmer amaranth plants in 2015 with similar trends observed in 2016. Palmer amaranth emergence was not affected by cover crop in either year.
• In the no management plots in 2016, Palmer amaranth biomass was reduced by narrow soybean row widths, while cover crop had no effect.
• There was no significant difference in yield between the low management and high management plots in 2015. In 2016, high management plots yielded 8.5 bu A-1 more than the low management plots. Significant reductions in yield occurred in the no management plots in both years.

Summary
Overall, cereal rye had minimal effects on Palmer amaranth control, regardless of termination method. However, cereal rye had no adverse effects and the observed suppression of winter annuals and early summer annuals indicates it may be beneficial for control of other weeds, such as horseweed (marestail). From this research, we recommend planting soybean in 7.5-inch row widths, as they lowered the duration of emergence and suppressed the growth of Palmer amaranth. The most effective management strategy for control of Palmer amaranth was to use an effective residual PRE followed by a POST application of Liberty paired with a second residual herbicide. A late POST application of Liberty may be needed for high populations or late rainfall events to control late-season Palmer amaranth emergence. This research will continue to be presented to Michigan growers and used to provide future recommendations to help manage this devastating weed problem.