Legume Futures Resource Centre
Title: Forage legumes in a multi-species grassland
Topic area: (choose one or more from this list or add a new topic)
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field performance and agronomy – including crop development, growth, yield,
resource capture
nitrogen fixation (field)
nitrogen cycle/balance in legume cropping systems
Start and ends dates: 01-11-2007 until 30-06-2011
Funder: International Centre for Research in Organic Food Systems (ICROFS)
Main investigator:
 name: Karin Pirhofer-Walzl, PhD
 address: Department of Agriculture and Ecology/Crop Science; Copenhagen
University, Højbakkegård Allé 13, 2630 Taastrup, Denmark
 telephone: +45-50596127
 email: karin.pirhofer@gmail.com
Other investigators:
Associate Professor Jesper Rasmussen, PhD; jer@life.ku.dk; Phone: +4535333456; Address: Department of Agriculture and Ecology/Crop Science;
Copenhagen University, Højbakkegård Allé 13, 2630 Taastrup, Denmark
Associate Professor Henning Høgh-Jensen, PhD
Centre Director for the Coordination Unit for Research in Climate Change
Adaptation; hhj@dmu.dk; Phone: +45-871 58547; Address: Department of
Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde,
Denmark
Senior Scientist Jørgen Eriksen, PhD; E-mail: jorgen.eriksen@agrsci.dk; Phone:
+45-87157672; Address: Department of Agroecology - Organic Matter, Aarhus
University, Blichers Allé 20; 8830, Tjele, Denmark
Summary of project
Background: Multi-species grassland mixtures, comprising grasses, legumes and
herbs, may have a potential to improve common grasslands consisting of low plant
diversity. The legume component of a grass-legume mixture contributes to nitrogen
(N) self-sufficiency of the grassland because of its ability for symbiotic N2 fixation,
which allows reduced fertilizer application. Several studies present a positive plant
diversity-productivity relationship for temporary European grasslands. Increased soil
nutrient use in grasslands with higher plant diversity may be one explanation, where,
for example, deep-rooted plant species enable nutrient uptake from deep soil layers.
Aims: The objective of this Ph.D. study was to quantify the performance of multispecies grassland mixtures comprising grasses, legumes and herbs in terms of three
nutrient processes: 1) mineral accumulation, 2) nitrogen transfer and 3) nitrogen
uptake.
Key words: grassland, Medicago sativa L., Trifolium repens L., Trifolium pratense L.,
Lotus corniculatus L., 15N methodology, 15Nitrogen transfer, 15Nitrogen uptake, N2
fixation, macrominerals, microminerals
Methods: Three field experiments were conducted in Denmark: two on a loamy-sandy
site and one on a sandy-loamy site. 15N methodology was used to trace nitrogen
through the plant-soil system and to measure N2 fixation.
Results: The three experiments demonstrated that multi-species grassland mixtures
have a potential as mineral-rich ruminant fodder as well as in increasing sustainability
in terms of efficient nitrogen (N) use. Four forage herbs on average had greater
concentrations of most macrominerals and some microminerals than that of grasses
and forage legumes. Furthermore, legumes contributed to N fertilization of each plant
species in a multi-species grassland. Deep-rooted plant species did not improve soil N
access in deep soil of a multi-species grassland. However, total 15N uptake indicated
that mixture of deep- and shallow-rooted plant species had greater 15N uptake values
compared with pure stands.
Main findings: Legumes played a strong role in the tested multi-species mixtures of
this Ph.D. study. While they generally showed similar or slightly lower mineral
concentrations than herbs, they imported N into the grassland system because of their
ability to fix symbiotically large amounts of N. This N was partly relocated to
neighbouring plants and may have stimulated grasses to absorb more N from the
shallow soil layer (0.4 m depth).
Implications/consequences: This study showed that multi-species grassland mixtures
have the potential to improve the common simple grass or grass-legume mixtures by
reducing the need for external mineral supplementation and by more efficient N use.
Yet to use varying plant diversity as a management tool in an agricultural system
based on grasslands, more knowledge from grass-legume-herb mixtures to animal
performance is needed.
References (reports / papers / files):
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Pirhofer-Walzl K, Rasmussen J, Høgh-Jensen H, Eriksen J, Søegaard K and
Rasmussen J (2011) Nitrogen transfer from forage legumes to nine
neighbouring plants in a multi-species grassland. Plant and Soil, DOI:
10.1007/s11104-011-0882-z
Pirhofer-Walzl K, Søegaard K , Høgh-Jensen H, Eriksen J, Sanderson MA,
Rasmussen J and Rasmussen J (2011) Forage herbs improve mineral
composition of grassland herbage. Grass and Forage Science, 66: 415-423
Further information on the project
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English summary and table of contents of the PhD thesis. Please contact Karin
Pirhofer-Walzl (karin.pirhofer@gmail.com) for the whole PhD thesis or
references.
Size of the file: 921 KB
Summary of the content of the file:
This file contains a summary of the three-year PhD project that dealt with
multi-species grassland mixtures, comprising grasses, legumes and herbs,
which may have a potential to improve common grasslands consisting of low
plant diversity. The performance of multi-species grassland mixtures were
quantified on different nutrient processes…
END