Abstract
Abstract In grass–legume swards, biologically fixed nitrogen ( N ) from the legume can support the N requirements of the grass, but legume N fixation is suppressed by additional fertilizer N application. This study sought to identify a fertilizer N application rate that maximizes herbage and N yields, N fixation and apparent N transfer from white clover to companion grasses under intensive grazing at a site with high soil‐N status. During a 3‐year period (2011–2013), swards of perennial ryegrass and of perennial ryegrass–white clover, receiving up to 240 kg N ha −1 year −1 , were compared using isotope dilution and N ‐difference methods. The presence of white clover increased herbage and N yields by 12–44% and 26–72%, respectively. Applications of N fertilizer reduced sward white clover content, but the effect was less at below 120 kg N ha −1 . The proportion of N derived from the atmospheric N fixation was 25–70%. Nitrogen fixation ranged from 25 to 142 kg N ha −1 measured using the isotope dilution method in 2012 and from 52 to 291 kg N ha −1 using the N ‐difference method across all years. Fertilizer N application reduced the percentage and yield of fixed N. Transfer of N from white clover to grass was not confirmed, but there was an increased N content in grass and soil‐ N levels. Under intensive grazing, the maximum applied N rate that optimized herbage and N yields with minimal effect on white clover content and fixation rates was 60–120 kg N ha −1 .
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Claims 10
Claim · model-written summary
The presence of white clover increased herbage yield by 12–44% relative to perennial ryegrass swards.
- Taxon
- white clover
Trifolium repense0 - Treatment
- presence of white clovere0
- Outcome
- herbagee0
- Direction
- increasede0
- Value
- 12–44%e0
- Comparator
- perennial ryegrasse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of white clover increased herbage and N yields by 12–44% and 26–72%, respectively”
e1“swards of perennial ryegrass and of perennial ryegrass”
Claim · model-written summary
The presence of white clover increased N yield by 26–72% relative to perennial ryegrass swards.
- Taxon
- white cloverTrifolium repense0
- Treatment
- presence of white clovere0
- Outcome
- N yieldse0
- Direction
- increasede0
- Value
- 26–72%e0
- Comparator
- perennial ryegrasse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of white clover increased herbage and N yields by 12–44% and 26–72%, respectively”
e1“swards of perennial ryegrass and of perennial ryegrass”
Claim · model-written summary
N fertilizer application reduced the white clover content of the sward.
- Taxon
- white cloverTrifolium repense0
- Treatment
- Applications of N fertilizere0
- Outcome
- sward white clover contente0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Applications of N fertilizer reduced sward white clover content”
Claim · model-written summary
The proportion of N derived from atmospheric N fixation was 25–70%.
- Taxon
- white cloverTrifolium repenst0
- Outcome
- proportion of N derived from the atmospheric N fixatione0
- Value
- 25–70%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“white clover”
e0“The proportion of N derived from the atmospheric N fixation was 25–70%”
Claim · model-written summary
Nitrogen fixation ranged from 25 to 142 kg N per ha by the isotope dilution method in 2012.
- Taxon
- white cloverTrifolium repenst0
- Outcome
- Nitrogen fixatione0
- Value
- 25 to 142 kg N hae0
- Qualifier
- isotope dilution method in 2012e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“white clover”
e0“Nitrogen fixation ranged from 25 to 142 kg N ha”
e1“measured using the isotope dilution method in 2012”
Claim · model-written summary
Nitrogen fixation ranged from 52 to 291 kg N per ha by the N-difference method across all years.
- Taxon
- white cloverTrifolium repenst0
- Outcome
- Nitrogen fixatione0
- Value
- 52 to 291 kg N hae1
- Qualifier
- across all yearse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“white clover”
e0“Nitrogen fixation ranged”
e1“from 52 to 291 kg N ha”
e2“across all years”
Claim · model-written summary
Fertilizer N application reduced the percentage and yield of fixed N.
- Taxon
- white cloverTrifolium repenst0
- Treatment
- Fertilizer N applicatione0
- Outcome
- percentage and yield of fixed Ne0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“white clover”
e0“Fertilizer N application reduced the percentage and yield of fixed N”
Claim · model-written summary
Transfer of N from white clover to grass was not confirmed.
- Taxon
- white cloverTrifolium repense0
- Outcome
- Transfer of N from white clover to grasse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transfer of N from white clover to grass was not confirmed”
Claim · model-written summary
The N content of the grass increased.
Verbatim
e0“there was an increased N content in grass”
Claim · model-written summary
Under intensive grazing the maximum N rate that optimized herbage and N yields with minimal effect on white clover content and fixation was 60–120 kg N per ha.
- Taxon
- white cloverTrifolium repense0
- Outcome
- maximum applied N ratee0
- Value
- 60–120 kg N hae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the maximum applied N rate that optimized herbage and N yields with minimal effect on white clover content and fixation rates was 60–120 kg N ha”
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See all 27 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.