Intraspecific and Interspecific Competition in Sweet Corn

Competition among crop plants (i.e., intraspecific) and between crop and weed plants (i.e., interspecific) likely co-occurs in many sweet corn (Zea mays L.) fields; however, a fundamental understanding of the extent to which the crop is affected by the combination of these stresses is unknown. The objective of this work was to identify the extent to which seeding level influences the crop's tolerance to weed competition in terms of crop development, yield, and profitability. In field research in Illinois and Washington, two hybrids with different levels of tolerance to weed competition were planted each of 2 yr at five seeding levels each year and grown in the presence and absence of wild-proso millet (Panicum miliaceum L.). The crop's ability to tolerate intraspecific and interspecific competition was additive, as evidenced by no significant interaction between seeding level and weed competition for thermal time to mid-silk, marketable ear number, marketable ear mass, and gross profit margin to the rocessor. Losses in gross profit margin due to weed competition alone ranged from $ 2,400 to $ 8,100 ha(-1). Hybrids used in this work showed differential tolerance to interspecific competition, but of the seeding levels tested, neither hybrid was consistently more tolerant to intraspecific competition. Across years and hybrids, the seeding level that consistently did not delay silking but maximized marketable ear number, marketable ear mass, and gross profit margin to the processor was 70,000 and 88,200 ha(-1) in Illinois and Washington, respectively. Improving weed management efficacy and genetic tolerance to competition off er two approaches to improving sweet corn productivity.