rdf-syntax-grammar
mods:
  schema location: http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
  title info:
    title: Mechanical factors influencing cotton emergence through soil crusts
  name:
    name part: Chu, Yuan-Nan
    name part: 1958-
    role:
      role term: creator
  name:
    name part: Coble, Charlie G.
    role:
      role term: degree supervisor.
  name:
    name part: Hiler, Edward A.
    role:
      role term: degree committee member.
  name:
    name part: Jordan, Wayne R.
    role:
      role term: degree committee member.
  name:
    name part: LePori, Wayne A.
    role:
      role term: degree committee member.
  name:
    name part: Texas A & M University
    role:
      role term: degree granting institution.
  type of resource: text
  genre: bibliography
  genre: Academic theses.
  origin info:
    place:
      place term: xx
    date issued: 1989
    issuance: monographic
  language:
    language term: eng
  physical description:
    form: print
    extent: xiii, 158 leaves : illustrations ; 29 cm
  abstract: Soil crusting is a worldwide problem for obtaining good stands after planting. This study was conducted to evaluate effects of environmental physical conditions upon mechanical factors influencing seedling emergence from soil crusts. The factors include seedling emergence force and critical time, hypocotyl elongation and swelling, crust impedance, and critical penetration distance. Critical penetration distance is the distance of penetration by the seedling when maxim um crust impedance is encountered. Seedling emergence force was measured when the seedling was supported laterally. Maximum emergence force varied quadratically with increases in soil temperature and moisture. The highest force, 11.4 N was measured at 28.5 °C and -0.1 bar. Critical time decreased linearly with increasing temperature. Maximum emergence force increased linearly with the hypocotyl cross-sectional area, while calculated turgor pressures were 768, 756, and 518 kPa at -0.1, -0.3, and -3.0 bar, respectively. Emergence force was much less when lateral support was not provided. Compaction of the top soil increased emergence force. Hypocotyl elongation decreased with increasing downward load and increased with increasing soil temperature and moisture. Swelling index increased quadratically with increasing downward load. Total fresh weight decreased with increasing downward load and decreasing soil moisture. Hypocotyl swelling generated potential emergence forces exceeding downward loads in the tested range, 0 to 1.8 N.A lower soil moisture reduced potential emergence force and caused a faster slowing of force increase. Crust impedance was measured using a mechanical probe penetrating from below. Up to four-fold increases in probe size and twenty-fold increases in probe speed did not increase measured impedance of dried crust. Crust impedance increased exponentially with time as the crust dried. An increase in initial soil moisture and compaction increased crust impedance. The increase in crust i…
  note: by Yuan-Nan Chu.
  note: "Major subject: Agricultural engineering."
  note: Typescript (photocopy).
  note: Vita.
  note: Ph. D. Texas A & M University 1989
  note: Includes bibliographical references.
  subject:
    topic: Cotton
    topic: Seedlings
  subject:
    topic: Plant-soil relationships
  subject:
    topic: Seeds
    topic: Development
  subject:
    topic: Soil mechanics
  subject:
    topic: Soil temperature
  subject:
    topic: Agricultural Engineering
  subject:
    topic: Cotton
    topic: Seedlings
  subject:
    topic: Plant-soil relationships
  subject:
    topic: Seeds
    topic: Development
  subject:
    topic: Soil mechanics
  subject:
    topic: Soil temperature
  identifier: http://gateway.proquest.com/openurl
  identifier: https://hdl.handle.net/1969.1/DISSERTATIONS-1108933
  identifier: http://proquest.umi.com/pqdweb
  related item:
    location:
      url: http://gateway.proquest.com/openurl
  related item:
    location:
      url: https://hdl.handle.net/1969.1/DISSERTATIONS-1108933
  related item:
    location:
      url: http://proquest.umi.com/pqdweb
  record info:
    record content source: TXA
    record creation date: 901130
    record change date: 20220103134946.0
    record identifier: in00000995024
    language of cataloging:
      language term: eng