Stability of corn (Zea mays) velvetleaf (Abutilon theophrasti) interference relationships

The crop-weed interference relationship is a critical component of bioeconomic weed management models, Multi-year field experiments were conducted at five locations to determine the stability of corn-velvetleaf interference relationships across years and locations, Two coefficients (I and A) of a hyperbolic equation were estimated for each data set using nonlinear regression procedures, The I and A coefficients represent percent corn yield loss as velvetleaf density approaches zero, and maximum percent corn yield loss, respectively, The coefficient I was stable across years at two locations, but varied across years at one location, The coefficient A did not vary across years within locations, Both coefficients, however, varied among locations, Results do not support the use of common coefficient estimates for all locations within a region.