Authors

• R. Mirzaei
• M. Rostami
• M. Ovaysi
• M. Banayan Aval
• M. Bagestani

Abstract

In order to study yield loss percentage and weed threshold density in grain corn, an experiment was conducted in 2002 at the AgriculturalCollege, Ferdowsi University of Mashhad using a factorial arrangement of treatments using additive series in a randomized complete block design. Two factors were involved in the experiment, redroot pigweed density in five levels (0, 2, 4, 6 and 12 plant.m^-2) and corn density in three levels (7, 9 and 11
plant.m^-2). Two parameters hyperbolic model was fitted to seed yield loss of corn. Minimum seed yield loss percentages were 6.54, 4.35 and 4.1 at 7, 9 and 11 plant.m^-2 corn density, respectively. Minimum seed yield loss decreased by 37% when corn density increased from 7 to 11 plant.m^-2. Maximum seed yield loss was 50.43, 34.16 and 24.6% at 7, 9 and 11 plant.m^-2­ corn densities, respectively. When corn density increased from 7 to 11 plant.m^-2 maximum seed yield loss decreased by 51%. Increasing corn density caused the increment at weed threshold density, so that it increased by 35% and reached from 0.13 to 0.2 plant.m^-2. Also increasing corn density caused the increment at weed economic threshold density from 1.5 to 2.8 plant.m^-2. Generally, density had a significant effect on competition between redroot pigweed and corn and threshold density, and increment of corn density increased corn competitive ability and reduced damage of redroot pigweed.

Keywords

• redroot pigweed (Amaranthus retroflexus)
• corn (Zea mays)
• competition
• economic threshold