Intraspecific and interspecific competition in sweet corn

Authors: Williams, Martin; Boydston, Rick

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2012
Publication Date: 2/8/2013
Citation: Williams, M.M. II, Boydston, R.A. 2013. Intraspecific and interspecific competition in sweet corn. Agronomy Journal. 105(2):503-508.

Interpretive Summary: The sweet corn plant competes with neighboring crop plants (called intraspecific competition) and neighboring weed plants that escape control (called interspecific competition). These two types of competition exert stress on the crop, which can decrease productivity. This research was the first of its kind to quantify the dynamics between intraspecific and interspecific competition on sweet corn development, yield, and profitability. Field studies were conducted in Illinois and Washington, representing the major production regions (Midwest and Pacific Northwest, respectively) of processing sweet corn. Sweet corn was grown under a range of crop population densities with and without wild-proso millet, one of the most abundant weeds of sweet corn. Results showed that intraspecific and interspecific competition had an additive effect on sweet corn, whereby each type of stress was not influenced by the other. How well the crop tolerated neighboring crop plants varied by production region, with greater tolerance to crop neighbors observed in Washington relative to Illinois. The impact of this research is that it quantifies the benefit, measured in dollars, of improving both the effectiveness of weed management as well as the crop’s ability to tolerate to its own neighbors.

Technical Abstract: Competition among crop plants (i.e. intraspecific) and between crop and weed plants (i.e. interspecific) likely co-occurs in many sweet corn 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. n field research in Illinois and Washington, two hybrids with different levels of tolerance to weed competition were planted at five seeding levels each year and grown in the presence and absence of wild-proso millet. 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 processor. 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 ha-1 and 88,200 ha-1 in Illinois and Washington, respectively. Improving weed management efficacy and genetic tolerance to competition offer two approaches to improving sweet corn productivity.