Identification of optimum seedbed preparation and establishment using soil structural visualisation
Atkinson, Brian S. (2008) Identification of optimum seedbed preparation and establishment using soil structural visualisation. PhD thesis, University of Nottingham.
A key aspect of the condition of soil as a medium for growing plants is the soil physical environment under which germination, growth and establishment occur. Crucially this affects factors such as water content, oxygen availability and soil strength. The dynamics of soil physical properties, and in particular soil structure, of a range of soils and how they relate to plant establishment are considered in this thesis. By engineering a variety of seedbeds and contrasting soil structures using different cultivation techniques, from intensive (plough) to reduced (disc) strategies, significant differences in the physical properties of the soils in terms of volumetric water content, soil strength and bulk density and interactions with plant establishment were identified. A model for Soil Quality of Establishment (SQE) was developed to predict plant establishment based upon soil bulk density and cultivation practices which significantly accounted for c. 50% of the variation occurring across contrasting soil types and environmental conditions. It was hypothesized from this that the precise porous architecture (i.e. soil structure) plays a crucial role in plant establishment given soil bulk density was a significant factor in the SQE model. Utilizing X-ray Computed Tomography (CT) both at a macro (c.300μm) and meso (c.65μm) scale soil structure (in terms of: porosity, pore area and perimeter, elongation, nearest neighbour distance, ECD and pore distribution) were determined in a quantitative manner. Results showed significant decreases in plant populations with associated increases in the soil porosity, with strong links to the pore size, roughness and spatial distribution (accounting for soil-seed contact, water storage / flow and ease of plant / root movement within the soil). Preferred porosity conditions for establishment and yield occurred between 12 - 20 % porosity (at the meso scale). SQE prediction was significantly improved with the addition of structural properties accounting for c. 70 % variation in crop establishment across soil texture and seasonal variation. The further 30 % variation in crop establishment may be explained by unforeseen circumstances such as disease and weather but equally this may also be related to crop genetics, soil chemistry and or the biological activities within the soil.
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