The Effect of Self-Loading on the Mechano-Stability and Stalk Lodging Resistance of Plant Stems

Abstract

18Background: Stalk lodging (breaking of agricultural plant stalks prior to harvest) is a multi-19 billion dollar a year problem. Stalk lodging occurs when bending moments induced by a 20 combination of external loading (e.g. wind) and self-loading (e.g. the plant's own weight) exceed 21 the bending strength of plant stems. Previous biomechanical plant stem models have 22 investigated both external loading and self-loading of plants, but have evaluated them as separate 23 and independent phenomena. However, these two types of loading are highly interconnected and 24 mutually dependent. The purpose of this paper is twofold: (1) to investigate the combined effect 25 of external loads and plant weight on the displacement and stress state of plant stems / stalks, and 26(2) to provide a generalized framework for accounting for self-weight during mechanical 27 phenotyping experiments used to predict stalk lodging resistance. 28 Results: A method of properly accounting for the interconnected relationship between self-loading 29 and external loading of plants stems is presented. The interconnected set of equations are used to 30 produce user-friendly applications by presenting (1) simplified self-loading correction factors for 31 a number of common external loading configurations of plants, and (2) a generalized Microsoft 32 Excel framework that calculates the influence of self-loading on crop stems. The effect of self-33 loading on the structural integrity of wheat is examined in detail. A survey of several other plants 34 is conducted and the influence of self-loading on their structural integrity is also presented. 35 Conclusions: The self-loading of plants plays a potentially critical role on the structural integrity 36 of plant stems. Equations and tools provided herein enable researchers to account for the plant's 37 weight when investigating the flexural rigidity and bending strength of plant stems. 38 39 40 42 estimated to range from 5-20% annually [1,2]. Despite a growing body of literature surrounding 43 the topic of stalk lodging in wheat, barley, oats, and maize [3-7], a detailed study on the 44 interconnected relationship between external loading (e.g. wind) and self-loading (e.g. plant 45 weight) on stalk bending strength has not been reported. Previous biomechanical plant stem 46 models have examined the influence of morphology, material, and weight on stem failure, while 47 others have separately analyzed the effects of externally induced bending forces (e.g., wind) on 48 stem failure [3,4,8-15]. However, the effects of self-weight and external loads on stem failure are 49 inextricably connected. The bending moment induced from self-weight is a function of the 50 distance between the plant's base and its center of gravity. As external loads displace the center of 51 gravity away from the base of the stem, the bending moment induced from self-weight 52 increases. Although previous studies have independently looked at external loads [4,5,16] and 53 self-weight loading [3], the authors are not aware of previ...