Journal
AGRICULTURE ECOSYSTEMS & ENVIRONMENT
Volume 140, Issue 1-2, Pages 155-163Publisher
ELSEVIER
DOI: 10.1016/j.agee.2010.11.022
Keywords
Competition; COST 852; Facilitation; N uptake; Symbiotic N-2 fixation; Transgressive overyielding
Funding
- Swiss State Secretariat for Education and Research
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Concerted use of legumes and of functional diversity in grassland forage systems can provide major contributions to the challenges of agricultural systems being productive yet environmental friendly. Acquisition and transformation of nitrogen (N) resources by legumes and grasses were studied in a temperate grassland experiment near Zurich (Switzerland) to investigate mechanisms driving effects of functional diversity in mixed swards and to optimise mixtures for efficient resource use. Grass-legume interactions and N availability were varied by manipulating legume percentage of the sward (0-100%) and N fertiliser application (50,150 or 450 kg of N ha(-1) year(-1)). N-15 technology quantified N derived from symbiotic (Nsym) and non-symbiotic (Nnonsym) sources. Generally, acquisition of Nsym by the entire mixture was stimulated by grasses. As a result, strong overyielding of Nsym occurred (e.g. 75 and 114% for year 1 and 2 at N150) and mixtures with only 60% and 37% legumes (year 1 and 2) already attained the same Nsym yield as pure legume stands. Legumes stimulated Nnonsym acquisition by the entire mixture, largely via increased uptake by the grass component. Thus, overyielding of Nnonsym of 31% occurred in year 1 (N150). Mutual grass-legume interactions stimulated acquisition of Nsym, acquisition of Nnonsym and efficient transformation of N into biomass compared to either monocultures. These effects of functional diversity can substantially contribute to productive and resource efficient agricultural grassland systems and were maximised in mixtures with 40-60% legumes. (C) 2010 Elsevier B.V. All rights reserved.
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