Predicting the time to 50% seedling emergence in wheat using a Beta model
Wang, H., Cutforth, H., McCaig, T., McLeod, G., Brandt, K., Lemke, R., Goddard, T., Sprout, C. (2009). Predicting the time to 50% seedling emergence in wheat using a Beta model, 57(1), 65-71. http://dx.doi.org/10.1016/j.njas.2009.07.003
The timing of seedling emergence greatly affects growth and yield of wheat (Triticum aestivum L.) and a good growth model should predict it accurately. The Cropping System Model of the Decision Support System for Agrotechnology Transfer (DSSAT-CSM) is used worldwide for many different applications, but its simulation of the timing of seedling emergence of wheat is not satisfactory under certain circumstances. In order to improve the prediction of seedling emergence, we incorporated a newly developed non-linear model, the Beta model, into DSSAT-CSM. Simulation performances were tested using observations in spring wheat (cv. Thatcher) from 24 sites across North America over the period 1930-1954, which totalled 244 site-years. Observed days from sowing to 50% seedling emergence (DSE) ranged from 5 to 39. The DSSAT-CSM model underestimated DSE in most cases. The Beta model using daily air temperature markedly improved prediction of seedling emergence. When using hourly air temperature, the Beta model generally resulted in predictions similar to when daily air temperature was used. However, calculated hourly temperature improved the simulation when the daily air temperature was near the base temperature for germination/emergence. When temperature was adjusted using a DSSAT-CSM-calculated soil moisture factor for germination/emergence (WFGE), the prediction was not improved, which could be related to the inaccurate simulation of near-surface soil moisture and the calculation of WFGE. The performance of the Beta model using soil temperature at sowing depth was not as good as simulations using air temperature, suggesting that the simulated soil temperature might not have been accurate. To further improve the prediction it is necessary to improve the simulation of near-surface soil moisture and temperature and the calculation of WFGE. Further work could also be done to simulate the dynamics of seedling emergence. © 2009 Royal Netherlands Society for Agricultural Sciences.
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