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Evaluation and Modeling of Physical and Physiological Damage to Wheat Seeds under Successive Impact Loadings: Mathematical and Neural Networks Modeling

^a Dep. of Agricultural Technical Engineering, College of Aburaihan, Univ. of Tehran, Tehran, Iran
^b Dep. of Agricultural Machinery, Faculty of Agriculture, Univ. of Lorestan, Khorram-Abad, Iran. This paper is a part of a project funded by Iran National Science Foundation (Project No. 83103)

^* Corresponding author (jkhazaei{at}ut.ac.ir).

Threshing wheat (Triticum aestivum L.) at high speeds is the main reason behind abnormal seedlings and vigor reduction of the seeds. This problem is expected to be severe in head-stripper combines with successive impact loadings of stripping and threshing units. The aim of this study was to simulate the effects of impact velocities (IV), number of impact loadings (NL), and seed moisture content (MC) on percentage of physical damage (PPD) and percentage of loss in germination (PLG) to wheat seeds. Modeling the correlation between dependent and independent variables was performed using mathematical and artificial neural networks (ANN). The result showed that all the three independent variables significantly influenced PPD and PLG (P = 0.01). Increasing the IV from 5 to 30 m s^–1 caused an increase in PPD and PLG from 0.17 to 35.8% and from 0.37 to 19.9%, respectively. It was found that the seeds with higher MC could better withstand physical and physiological damage than those with lower MC. With an increase in NL from 1 to 3 times, the mean values of PPD and PLG were increased by 2.9 and 2.6 times, respectively. An ANN model with two hidden layers, trained with a back-propagation algorithm, successfully learned the relationship between the input and output variables. In comparison with regression models, ANN performed better when predicting PPD and PLG to wheat seeds.

Abbreviations: ANN, artificial neural networks • IV, impact velocity • MC, moisture content • NL, number of impact loadings on seeds • PD, physical damage • PLG, percentage of loss in germination • PPD, percentage of physical damage • RIPPD_IV, rate of increase in percentage of physical damage per unit increase in impact velocity • RIPPD_MC, rate of increase in percentage of physical damage per unit decrease in moisture content • SPRC, standardized partial regression coefficient

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Received for publication April 3, 2007.