Modeling Wheat Seedling Growth and Emergence: I. Seedling Growth Affected by Soil Water Potential

Abstract

Abstract To improve the prediction of wheat ( Triticum aestivum L.) emergence, an empirical model of wheat root and shoot growth, which takes into account the soil water potential effects, is proposed. Pregerminated seeds from a Moroccan wheat cultivar, Nesma 149, were used for laboratory experiments at a constant 22 °C temperature. Seminal root and shoot lengths were measured vs. time using a completely randomized design, for a clay loam soil (33.6% clay, 57.0% loam and 19.4% sand) at five water potentials: −0.02; −0.17; −0.39; −1.0; −1.31 MPa. Soil dry bulk density of aggregates ≤3 mm was 1000 kg m −3 and thus, soil mechanical resistance to root growth was regarded as a nonlimiting factor. Data were used to select satisfactory growth functions for seminal root axes and shoots and to estimate their empirical parameters. The monomolecular and Gompertz functions were retained for roots and aerial parts, respectively. Considering that the soil water potential in the root zone controlled the root elongation rate, we took into account the average soil water potential along the root axes for calculations. Furthermore, the effects of soil water potential on the estimated parameters of the models involved in the growth models were studied. Results showed that roots and shoots responded differently to soil water stress. After 17 d, total root lengths varied from approximately 600 mm to 300 mm for the −0.02 MPa and −1.31 MPa treatments, respectively, whereas shoot lengths were similar. Finally, the growth curves calculated with soil water potential as input were compared with observed results. The correlation coefficients between predicted and observed data varied from 0.77 to 1.00.