Biology, Ecology and Management of Common Waterhemp

These studies focused on examining the biology and ecology of common waterhemp. This research evaluates the effect shade may have on common waterhemp growth and seed production, what effect row spacing may have on common waterhemp, crop and tillage effects on common waterhemp, and construction of a non-linear model to help predict when management should be implemented. Plant biomass and seed production decreased as shade levels were increased to 40, 68 and 99%. Common waterhemp plants responded to reduced irradiance by increasing leaf area ratios and decreasing relative growth rates. Common waterhemp emergence over the course of the growing season was closely associated with hydrothermal time within each year. In the years 1997, 1998, 1999 and 2000 the percent of the original common waterhemp seed bank that remained in the tilled treatments was 40%, 31%, 10% and <1% respectively. No-tilled treatments showed more reduction in the number of seeds remaining than tilled treatments in the top 0--6 cm of the soil profile. Common waterhemp seed had the longest duration of emergence under no-tilled followed by tilled treatments in 1997. Common waterhemp from 1998 through 2001 needed less than half the hydrothermal time to reach 50% emergence than in 1997. Season-long common waterhemp interference reduced corn grain yield by 74% in two years of the study and 11% in the third. Common waterhemp that emerged at the V4 corn growth stage and competed until corn maturity reduced corn grain yield by 59% in two years of the study and 13% in the third. The effect of timing of common waterhemp emergence in relation to soybean yield was described using an exponential decline model. Yield loss decreased at a faster rate for the 19-cm row spacing than the 76cm row spacing as common waterhemp emergence was delayed. Common waterhemp that emerged after the V4--V5 and R1--R2 soybean growth stages did not reduce soybean yield in the 19-cm and 76-cm row spacing, respectively.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Steckel, Lawrence Edward

Contributors dc:contributor

• Christy L. Sprague

• Biology, Ecology

Language dc:language

eng

Identifier

(MiAaPQ)AAI3086185

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85010