The Effect of Lodging in Cereals on Morphological Properties of the Root-Soil Complex

The permanent displacement of plant stems from the vertical, known as lodging, affects all cereal species and is a major limiting factor on grain production worldwide. Two forms of lodging are recognised: stem lodging (when the stem base buckles) and root lodging (when the root-soil system fails). However, there is conjecture about the mechanism of how the root-soil system fails. This is mainly due to the difficulties associated with observing the process within its natural environment. To enable an investigation of root failure in situ, a method for collecting undisturbed soil cores containing the root system of cereal plants was developed. This involved impregnating the soil surrounding the roots with varnish to solidify the upper 100 mm of the root-soil complex. Samples were collected from winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.) grown on three different textural types: clay, silty loam and sandy loam at two planting densities (100 and 400 seeds/m). Once collected, the root-soil samples were re-impregnated with crystic resin in the laboratory, sectioned and each slice photographed. The resulting images were analysed using image analysis software to quantify differences in the size, shape and distribution of soil pores, together with the orientation and position of the below-ground part of the cereal stem and its crown roots. Analysis revealed that lodging has a significant effect on the total porosity of the three soils (p<0.01). Soil type and lodging together had significant (p<0.05) effects in the number of pores in the three soils, with soil type having the most significant effect (p<0.001). There was no significance of lodging on pore shape. This research is important as it permits examination of the root-soil complex as it occurs in the field and could hold the key to elucidating the mechanism of root-soil failure. Further, the outcome will help identify traits of roots that confer strong anchorage and represent significant advances in the development of genotypes and husbandry practices which enable crops to withstand adverse weather conditions without the use of growth retardants.