Modelling variety dependant least limiting water range: assessing the limits to root elongation in field soil.

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Compaction is listed as one of the major issues affecting many UK soils and can limit crop yields. Compaction affects the integral network of soil particles and pores that comprise field soil, reducing the pore space and affecting the water holding capacity and the hydraulic properties of soil. The soil texture and moisture content can also influence the hardness of the soil. Root elongation is restricted if the soil is too hard for the roots to penetrate, lacks oxygen or is under water deficit conditions. The response of an average plant / root to these variable properties can be captured graphically as the least limiting water range (LLWR, See Figure: the range of water in a specific soil that does not significantly limit plant growth, calculated using standard growth limiting factors of soil strength (SS), wilting point (WP) and oxygen deficiency (OD). )This calculation takes into account average limits of soil strength, oxygen deficiency and water deficit. However crop varieties differ particularly in their root elongation responses to differences in water deficit and soil strength. These differences are underpinned by variances in root traits and how these relate to the pore structure, water availability and soil strength (e.g. Border cells assist in elongation in compacted soil). There is therefore an integral link between plant trait effectiveness in assisting in plant performance and the soil structure. The aim of this project is to develop a model based on the LLWR visual approach that allows the effect of root: soil interactions on individual varieties to be taken into account based on the rooting traits. The model will assist in assessing whether differences in variety responses to soil tillage are linked to underlying variances in the limiting water ranges for the specific varieties and their response to complex soils.