Competition and growth of a grass–legume mixture fertilised with nitrogen and phosphorus: effect on nutrient acquisition, root morphology and symbiosis with soil microorganisms

Abstract

Achieving a fast initial growth is crucial for legumes because grasses grow more rapidly and compete much better with forbs. In a pot experiment with a nutrient-deficient soil, we added nitrogen (N), phosphorus (P) and N + P to pure and mixed stands of Lotus tenuis and Festuca arundinacea and investigated the effects of on plant growth, nutrient uptake and symbiotic associations with arbuscular mycorrhizae and rhizobia. Plant yield, N and P acquisition, mycorrhizal colonisation, rhizobial nodulation and root length were measured and root diameter and root surface area were calculated after two harvests. Species responded differently to specific nutrients when grown pure or mixed. Comparing pure with mixed stands in soils fertilised with P and N + P, L. tenuis showed decreased shoot and particularly root biomass, whereas F. arundinacea showed increases in both biomasses. This suggests that the competitiveness of the grass with the legume increased upon P and N + P addition. In mixed stands, F. arundinacea produced 51–64% of the total shoot biomass and 69–74% of the total root biomass with P and N + P, respectively. Root length and root surface area were greater and the roots thinner in F. arundinacea than in L. tenuis. Addition of P and N + P increased rhizobial nodulation in legume roots but decreased mycorrhizal colonisation in both plants. Supply of N does not necessarily favour grasses, whereas P supply favours legumes. Optimisation of P nutrition might help to maximise N inputs into grasslands by symbiotic N-fixation and decrease inputs of inorganic N by fertilisation.

Rhizobium-Linked Nutritional and Phytochemical Changes Under Multitrophic Functional Contexts in Sustainable Food Systems

“…Competition is the contentious interaction for limited resources between organisms that is characterized by efficient resource consumption (exploitation) or harmful effects to the adversary (interference) (Ghoul and Mitri, 2016). Competition for nutrients and space is a key form of antagonistic interaction that affects rhizobia and host plants (Postma et al, 1990;Poole et al, 2018), in both independent and symbiotic states of the two organisms (Mendoza et al, 2016;Hortal et al, 2017;Lardi et al, 2017). Non-nodulating strains of Rhizobium leguminosarum compete with the nodulating types for infection sites, causing delay in development and function of root nodules (Lie et al, 1988), which reduces the performance of leguminous host plants (Gano-Cohen et al, 2016).…”

High-throughput, image-based phenotyping reveals nutrient-dependent growth facilitation in a grass-legume mixture

“…Facilitation of N uptake [ 21 ] and growth in grass-legume mixtures is the primary motivation for intercropping in pastoral agriculture. N and P fertilization can have varying effects on this relationship [ 57 ], as well as the length of time that species interact under particular nutrient conditions [ 58 ]. We successfully measured growth facilitation using HTP, revealing a yield benefit for both grasses and legumes ( Fig 3a ).…”

“…relationship [57], as well as the length of time that species interact under particular nutrient conditions [58]. We successfully measured growth facilitation using HTP, revealing a yield benefit for both grasses and legumes (Fig 3a).…”

Understanding Species Traits and Biodiversity Indices to Solve Problems Associated with Legume Persistence in Cropping Systems

“…On the other hand, P increases nodule mass. Work by Mendoza et al [23] has revealed that optimum supply of P triggers a positive growth response of legumes integrated with grass crops unlike pure stand. However, P may favor grass shoots and root biomass accumulation at the expense of the development of congregate legumes.…”