Glyphosate-resistant horseweed populations have become more widespread in the state and are now a significant management issue in western PA and the Northern Tier. In addition to glyphosate- or glyphosate and ALS-inhibitor resistance, horseweed is challenging to control because of variable emergence patterns.

Corn grown following alfalfa stands that are 2 years and older (and contained at least 50% alfalfa) require no nitrogen (N) fertilizer on many soils. Red clover N credits are less than for alfalfa.