Phosphorus (P) is a limiting nutrient in many natural and cultivated ecosystems due its poor availability for plants in soil. P inputs when applied in excess of plant demand often show a low P balance use efficiency, which can lead to an accumulation of P in fertilised soil. Multispecies systems such as cover crops or intercropping may offer opportunities to improve the plant utilisation of soil P. Plant P acquisition strategies and later P release from litter (crop residues) involved in P cycling and availability are driven by complex plant-soil feedbacks. Understanding these plant soil feedbacks requires insights into interactions among functional traits involved in P acquisition as well as litter trait effects on microbial P and P availability. As such we aimed to highlight the main plant traits and their interactions involved in P acquisition and litter traits involved in P release from litter to understand P cycling in multispecies systems. Traits interactions involved in P acquisition were investigated in controlled conditions using a wide gradient of morphological (%FR, RLD, SLA, SRL) and physiological traits (carboxylate exudation, phosphomonoesterase activity). Litter traits influence on litter P release was then investigated in a subsequent plant growth and soil incubation study.
Results/Conclusions
Multiple tradeoffs and interactions between traits involved in P acquisition were observed, in particular between thicker and thinner roots, with thicker roots exhibiting increased physiological traits expression and thus potentially having preferred access to poorly available soil P. Our results are in accordance with the notion of an economic spectrum of root traits. Furthermore, multivariate analysis highlighted uneven convergence toward four functional P acquisition strategies, potentially exploiting different soil P pools. These new results provide important insights toward the higher P acquisition observed in functionally diverse systems and open perspectives for managing P cycling in multispecies systems. C:P ratio turns out to be a pivotal litter trait in understanding the influence of litter on P availability. In P limited soil contexts, litter addition may result in significant temporary decrease in P availability due to microbial immobilization, as observed for litter with high C:P ratio. However, this immobilizing effect was attenuated with time and disappeared after about 3 months. Overall our results demonstrate a potential for enhancing P availability and P cycling efficiency in multispecies systems via improved designs thanks to a better understanding of their functioning and the plant-soil feedbacks involved.