Rye biomass of 5200 kg ha⁻¹ reduced Palmer amaranth emergence by 50%.

Rye biomass of 5370 kg ha⁻¹ reduced light at the soil surface by 50%.

Maximum spring rye biomass occurred when it was planted prior to the middle of November.

50% reduction in spring rye biomass when rye was planted in the middle of December.

Increasing the rye seeding rate did not overcome delays in planting.

Nitrogen increased rye biomass 23–33%, when averaged over all planting dates.