Degree Type

Dissertation

Date of Award

1984

Degree Name

Doctor of Philosophy

Department

Agronomy

Abstract

The use of no-till and other reduced tillage systems has increased substantially over the past several years. However, no studies have been reported in which large numbers of unselected genotypes were grown in no-till and conventional tillage to examine the effect of tillage systems upon selection of maize (Zea mays L.) genotypes;In this study, three sources of maize genotypes were evaluated in two tillage systems. The sources included were: (1) 100 S(,1)-lines from BS22(R)Cl, an elite synthetic population adapted to northern Iowa, (2) 100 S(,1)-lines from BS13(SCT)C6, a BSSS(HT)C7 derived synthetic population improved through six cycles of S(,1)-line per se recurrent selection for cold tolerance, and (3) 60 commercial hybrids. The two tillage systems used were a strict no-till system, and a conventional tillage system with fall plowing. S(,1)-lines were evaluated in 5 environments, and hybrids were evaluated in 4 environments. A split-plot experimental design was used, with tillage systems as main plots;Traits which had significant genotype by tillage or genotype by tillage by environment interactions in a combined anova over tillage systems and environments, for at least one of the populations, included: percentage emergence, early plant height, days to 50% pollen shed, stay green, grain yield, percentage stalk lodging, percentage root lodging, and final stand. For the hybrid genotypes, interactions of genotypes with tillage were not significant for grain yield, percentage grain moisture, percentage stalk lodging, percentage root lodging, or final stand;Different lines were selected in no-till than fall plow, based on grain yield, in both populations. For BS22(R)Cl, a significant difference between selected groups was consistent over years. Hybrid genotypes had no significant differences between no-till and fall plow selections. These data indicated that no-till yield evaluation during initial selection stages would be feasible to improve no-till maize yields.

DOI

https://doi.org/10.31274/rtd-180813-11891

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Keith Elling Newhouse

Language

en

Proquest ID

AAI8423662

File Format

application/pdf

File Size

317 pages

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