RootOutP · Investigating interactions between plant roots and phosphorus in soil

Investigating interactions between plant roots and phosphorus in soil

Phosphorus (P) is a scarce resource that is critical for crop production, but it is not being used sustainably. Excessive past fertiliser applications mean large amounts of P have accumulated in soil, losses of which are of major environmental concern. Nonetheless, the majority of soil-P exists in pools of very low bioavailability to plants, due to the high reactivity of P in soil. Increasing the ability of plants to take up P from applied sources (fertilisers) and from accumulated soil reserves would allow for reductions of fertiliser use and decreased potential P losses to the environment. Through evolution, plant roots have adopted several strategies to improve P capture, including: 1) architectural traits that affect the spatial exploration of the soil profile; 2) adaptive (plastic) responses to zones of high P supply (e.g. around fertiliser granules); and 3) physiochemical alteration of the environment in their rhizosphere. A challenge for the research community is to evaluate these properties and their potential benefits to cropping systems. As soil is inherently opaque, these traits are hard to study. Our current knowledge is fragmented because studies have generally used destructive sampling techniques, artificial media, and experimental setups making observations in 1D or 2D. Further advances of our understanding require in-situ visualization and quantification in real soil. This project delivered such in-situ information in the pursuit of ultimately selecting crops with benefitial root traits and developing crop systems that make better use of applied and accumulated soil P. Specifically, the overarching objective of the project was to understand how root traits and distribution are affected by the spatial distribution of P availability, and vice-versa (Fig. 1), by achieving the following objectives: 1. Demonstrate how root system architecture of contrasting genotypes affects the response to heterogeneously distributed P fertiliser in time 2. Determine how contrasting genotypes respond plastically to a fertiliser P band and relate this to soil chemical properties (labile P, speciation of elements) across the soil-fertiliser interface 3. Demonstrate how citrate exudation along a root axis affects soil pH and availability of P for contrasting genotypes (high citrate efflux /no citrate efflux)

Data: CORDIS, © European Union