Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2013
Publication Date: 4/20/2014
Citation: Al-Mulla, Y.A., Huggins, D.R., Stockle, C.O. 2014. Simulation of emergence of winter wheat in response to soil temperature, water potential and planting depth. Transactions of the ASABE. 57(3):1-15. Interpretive Summary: Seedling emergence is a critical stage in the establishment of dryland wheat particularly under drought conditions. Successful establishment of wheat is dependent on soil temperature, water status and planting depth all of which can vary considerably in a field. Our objectives were to: 1) measure the effect of soil temperature, water and planting depth on seedling emergence of winter wheat; and 2) develop a population-based hydrothermal model to estimate time and percentage of emergence of winter wheat. We were able to relate soil water and temperature status as well as planting depth to wheat emergence characteristics. These data were used to develop a useful wheat emergence model. This research will be useful to crop modelers and others interested in predicting how soil conditions and planting depth effect wheat establishment under dryland conditions.
Technical Abstract: Seedling emergence is a critical stage in the establishment of dryland wheat. Soil temperature, soil water potential and planting depth are important factors influencing emergence. These factors have considerable spatio-temporal variation making it difficult to predict the timing and percentage of wheat seedling emergence. Our objectives were to: 1) measure the effect of soil temperature, water potential and planting depth on seedling emergence of winter wheat; and 2) develop a population-based hydrothermal model to estimate time and percentage of emergence of winter wheat, planted at a given soil depth, in response to soil temperature and water potential. Decreasing soil water potential from 0 to -1 MPa delayed emergence of Moro, Buchanan, and Rod by 13, 14, and 18 days after planting and prolonged the time to reach maximum emergence by 19, 21, and 27 days after planting, respectively. Decreasing soil temperature from 25 to 5°C delayed the average starting emergence of the three wheat cultivars by 19 days and their average maximum emergence by 25 days after planting. Increasing soil planting depth from 5 to 10 cm delayed starting emergence time for Moro, Buchanan, and Rod by 6, 4, and 7 days while maximum emergence was delayed by 12, 16, and 9 days after planting, resp. Increasing the planting depth from 5 to 15 cm, hindered the three cultivars from reaching 50% emergence. A hydrothermal time emergence model was developed that estimated observed emergence with 154 out of 207 data points having a RMSE less than or equal to 15%, whereas 19% of the simulated results did not exceed 19% RMSE while only 7% of the simulated data had RMSE greater than 20%.