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

GARCÍA, ILEANA; MENDOZA, RODOLFO; DEPALMA, DANIELA; FERNÁNDEZ LÓPEZ, CAROLINA

CROP & PASTURE SCIENCE

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2016 vol. 67 p. 629 - 640

1836-5795

Achieving a fast initial growth is crucial for legumes because grasses grow more rapidly and compete muchbetter with forbs. In a pot experiment with a nutrient-deficient soil, we added nitrogen (N), phosphorus (P) and N+ P to pureand mixed stands of Lotus tenuis and Festuca arundinacea and investigated the effects of on plant growth, nutrient uptakeand symbiotic associations with arbuscular mycorrhizae and rhizobia. Plant yield, N and P acquisition, mycorrhizalcolonisation, rhizobial nodulation and root length were measured and root diameter and root surface area were calculatedafter two harvests. Species responded differently to specific nutrients when grown pure or mixed. Comparing pure withmixed stands in soils fertilised with P and N+ P, L. tenuis showed decreased shoot and particularly root biomass, whereasF. arundinacea showed increases in both biomasses. This suggests that the competitiveness of the grass with the legumeincreased upon P and N+ P addition. In mixed stands, F. arundinacea produced 51?64% of the total shoot biomass and69?74% of the total root biomass with P and N+ P, respectively. Root length and root surface area were greater and theroots thinner in F. arundinacea than in L. tenuis. Addition of P and N+ P increased rhizobial nodulation in legume rootsbut decreased mycorrhizal colonisation in both plants. Supply of N does not necessarily favour grasses, whereas P supplyfavours legumes. Optimisation of P nutrition might help to maximise N inputs into grasslands by symbiotic N-fixationand decrease inputs of inorganic N by fertilisation.