University of Illinois Urbana-Champaign

Crop-water stress index models for cool season turfgrasses

Martin, Dennis Loren

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Description

Title
Crop-water stress index models for cool season turfgrasses
Author(s)
Martin, Dennis Loren
Issue Date
1990
Doctoral Committee Chair(s)
Wehner, D.
Department of Study
  • Agriculture, Agronomy
  • Engineering, Agricultural
Discipline
  • Agriculture, Agronomy
  • Engineering, Agricultural
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Agriculture, Agronomy
  • Engineering, Agricultural
Language
eng
Abstract
  • Crop Water Stress Index (CWSI) technology has shown potential in improving irrigation timing as it determines timing based on the plant's need. Research was conducted to better apply this technology to turf management. The objectives of this study were (i) to determine the complexity of model needed to accurately calculate the CWSI, (ii) to determine if a single model is appropriate across both Kentucky bluegrass (Poa pratensis L.) (KB) and creeping bentgrass (Agrostis palustris Huds.) (CB), and (iii) to evaluate the performance of CB when managed under different CWSI models.
  • Models were developed for predicting the upper and lower limits of the canopy-air temperature difference ((T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm UL}$ and (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm LL}$) of five KB and one CB for use in calculating the empirical CWSI. Cultural regimes were 196 kg N ha$\sp{-1}$ yr$\sp{-1}$ for all grasses, and cutting heights of 9.5 and 48 mm for CB and KB respectively.
  • Use of vapor pressure deficit (VPD), net radiation (R$\sb{\rm n}$), and wind speed (WS) was required to accurately predict (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm LL}$. When tested on a validation data set, an energy balance equation accounted for less variation in T$\sb{\rm c}$-T$\sb{\rm a}$ of turf than a model using VPD, R$\sb{\rm n}$, and WS. Net radiation and WS terms were required to best predict (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm UL}$.
  • Irrigation of CB was scheduled by 4 CWSI models at 3 CWSI set points (0.25, 0.50, and 0.75). Irrigation (1.3 cm) was applied when the CWSI was $\geq$ the CWSI set point. Variables groups used to calculate (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm LL}$ in models I-III were VPD; VPD and R$\sb{\rm n}$; and VPD, R$\sb{\rm n}$, and WS. Model I calculated (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm UL}$ by solving the equation for (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm LL}$ where the vapor pressure gradient equals 0. Variables used to calculate (T$\sb{\rm c}$-T$\sb{\rm a}$)$\sb{\rm LL}$ in models II and III were R$\sb{\rm n}$; and R$\sb{\rm n}$ and WS. Model IV utilized an energy balance approach.
  • The number of irrigation events, quantity of water applied, and color ratings of CB declined with increasing model complexity and increasing value of the CWSI set point.
  • At locations where environmental conditions are variable, empirical CWSI models must account for the effects of VPD, R$\sb{\rm n}$, and WS in order to accurately assess the CWSI. A single CWSI model may be appropriate for KB cultivars managed alike. A separate CWSI model for CB appears necessary. Color of CB depends on both CWSI model type and CWSI at which irrigation is applied.
Type of Resource
text
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Copyright and License Information
Copyright 1990 Martin, Dennis Loren

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