Dissertation
Evaluating simple transpiration-based models of crop productivity
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2006
DOI:
https://doi.org/10.7273/000005628
Abstract
There is a renewed interest in evaluating crop productivity using simple transpiration–based models of biomass accumulation. Transpiration–use efficiency (w), defined as the ratio of biomass (B) produced per unit water transpired (T), has been widely used to evaluate crop performance under limited water supply. Simple approaches to asses w have been used including: 1) = Dkw aDa and 2) = ETo TEkw o ; where Da k and ETo k are crop-dependent parameters. The concept is that normalization by Da or ETo would account for the effects of climate variations on w, while Da k or ETo k would be reasonably constant across diverse environments. However, the evaluation of the transferability of these parameters is not simple due to the scarcity of experimental values and the lack of consistency of the methodology used in the available experiments. For this reason we have developed and tested a canopy transpiration and photosynthesis model (CTP) to obtain simulated values of w, Da k and ETo k in different locations with a consistent methodology. Model simulations were compared with evapotranspiration estimated with weighing lysimeters for non stressed wheat and maize. Results showed good agreement between observed and simulated transpiration values for both crops, with the simulated values tracking well the daily fluctuations of the observed values. Daily values of simulated transpiration–use efficiency (w) were compared with observed values from literature and showed that the average and standard deviation of the simulated values were within the range of the observed data. The model was then used to evaluate the transferability of Da k and ETo k values for wheat and maize across eight world locations with contrasting climate. The results indicated that Da k and ETo k (maize) are not constant parameters; suggesting that calibration in contrasting climates would be desirable. However, a consistent trend of change of the values of these parameters as a function of Da or ETo was found, which can be represented by mathematical functions, allowing the possibility of transferring Da k and ETo k values across climatic conditions. Verification of these equations with field data was performed. The simulation–based equations to estimate w and Da k of wheat and maize, and ETo k of maize appeared to be robust estimators of observed values, while ETo k of wheat was better represented by a single value across climatic conditions.
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Details
- Title
- Evaluating simple transpiration-based models of crop productivity
- Creators
- Cristian Kremer
- Contributors
- Claudio O. Stockle (Chair)Joan Qiong Wu (Committee Member) - Washington State University, Department of Biological Systems EngineeringRobert G Stevens (Committee Member) - Washington State University, Department of Crop and Soil Sciences
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Biological Systems Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 133
- Identifiers
- 99901054737501842
- Language
- English
- Resource Type
- Dissertation