Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
MICROMETEOROLOGY OF SORGHUM AT TWO ROW SPACINGS (ROUGHNESS SUBLAYER, ENERGY BALANCE, HORIZONTAL INHOMOGENEITY, GUST, CIRCULATION)
Abstract
Changes in water use due to changing row spacing have been observed for sorghum. Mechanisms have been proposed to explain how surface horizontal inhomogeneities may cause this effect. Observations within and above canopy-like surfaces suggest that, at some degree of surface inhomogeneity, one-dimensional assumptions are invalid. Research was undertaken to study the effect of row spacing on the mechanisms of transfer that occur within and above a sorghum canopy. Two contrasting row spacings were compared (0.76 and 1.52 m) in fields with near-equal populations. Crop production and water use, energy balance components, within-canopy temperatures, and above-canopy temperature and vapor pressure were compared for the two fields. The narrow-row field had a greater yield and slightly less water use. These effects, however, were not clearly attributable to row spacing. In the daytime the net radiation was greater in the narrow-row field apparently due to longwave radiation loss from the hot mid-row soil between the wide rows. The magnitude of soil heat flux density was greater in the wide-row field for this same reason. Consequently, during the latter part of the season, more energy was available to the narrow-row field and latent energy flux density was greater there. Within-canopy air temperature patterns were relatively more one-dimensional in the narrow-row field and two dimensional in the wide-row field. Horizontal temperature gradients were larger and more persistent in the wide-row field. A cool mid-cavity region occurred at midday between the wide rows suggesting gust penetration of air from above the canopy. Daytime temperature patterns suggest a circulation between the rows. Temperature and vapor pressure profiles did not indicate the existence of the roughness sublayer over the 0.76-m rows. A roughness sublayer deeper than 1.75 m occurred above the 1.52-m rows (the sorghum was 1.30-m tall). Data support horizontal inhomogeneity and convection, two mechanisms proposed to explain the formation of the roughness sublayer.
Subject Area
Biophysics
Recommended Citation
GRASER, ELIZABETH ANNETTE, "MICROMETEOROLOGY OF SORGHUM AT TWO ROW SPACINGS (ROUGHNESS SUBLAYER, ENERGY BALANCE, HORIZONTAL INHOMOGENEITY, GUST, CIRCULATION)" (1985). ETD collection for University of Nebraska-Lincoln. AAI8516872.
https://digitalcommons.unl.edu/dissertations/AAI8516872