Abstract
Abstract Nitrogen fixation (acetylene reduction) rates were monitored for 2 years in pastures receiving 100–150 kg N/ha per year as urea and in a control pasture. Applying 100 kg of fertiliser N in 2 applications reduced annual nitrogen fixation from 100 kg N/ha to 70 kg N/ha. Clover yields were reduced less — on average by 8% when only 100 kg N was applied preceding and during measurement, and by 17% averaged over all farmlets. Hence the major effect of nitrogen fertiliser on clovers was to substitute mineral nitrogen for nitrogen fixation. There was a high level of utilisation of the pastures, which would have minimised the reduction in clover yields expected from increased grass competition. An annual nitrogen fertiliser input of 150 kg N/ha reduced clover yields the following summer more than did an input of 100 kg N/ha. Nitrogen fixation was similar in both nitrogen treatments, because of an increase in nitrogen fixation per unit clover grown at the higher nitrogen level.
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Claims 7
Claim · model-written summary
Applying 100 kg of fertiliser N in 2 applications reduced annual nitrogen fixation from 100 kg N/ha to 70 kg N/ha relative to a control pasture.
- Treatment
- Applying 100 kg of fertiliser N in 2 applicationse0
- Outcome
- annual nitrogen fixatione0
- Direction
- reducede0
- Value
- from 100 kg N/ha to 70 kg N/hae0
- Comparator
- control pasturee1
TrifoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Applying 100 kg of fertiliser N in 2 applications reduced annual nitrogen fixation from 100 kg N/ha to 70 kg N/ha”
e1“and in a control pasture”
t0“nitrogen fertiliser on clover”
Claim · model-written summary
Clover yields were reduced on average by 8% when only 100 kg N was applied preceding and during measurement.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Clover yields were reduced less — on average by 8% when only 100 kg N was applied preceding and during measurement”
Claim · model-written summary
Clover yields were reduced by 17% averaged over all farmlets.
- Treatment
- nitrogen fertilisert0
- Outcome
- Clover yieldse0
- Direction
- reducede0
- Value
- 17%e0
- Qualifier
- averaged over all farmletse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Clover yields were reduced less — on average by 8% when only 100 kg N was applied preceding and during measurement, and by 17% averaged over all farmlets”
t0“nitrogen fertiliser on clover”
Claim · model-written summary
An annual nitrogen fertiliser input of 150 kg N/ha reduced clover yields the following summer more than an input of 100 kg N/ha.
- Treatment
- annual nitrogen fertiliser input of 150 kg N/hae0
- Outcome
- clover yieldse0
- Direction
- reducede0
- Qualifier
- the following summere0
- Comparator
- input of 100 kg N/hae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An annual nitrogen fertiliser input of 150 kg N/ha reduced clover yields the following summer more than did an input of 100 kg N/ha”
Claim · model-written summary
Nitrogen fixation was similar in the two nitrogen treatments.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fixation was similar in both nitrogen treatments”
t0“nitrogen fertiliser on clover”
Claim · model-written summary
Nitrogen fixation per unit clover grown increased at the higher nitrogen level, which explains the similar fixation in both treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“because of an increase in nitrogen fixation per unit clover grown at the higher nitrogen level”
Claim · model-written summary
The major effect of nitrogen fertiliser on clovers was to substitute mineral nitrogen for nitrogen fixation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hence the major effect of nitrogen fertiliser on clovers was to substitute mineral nitrogen for nitrogen fixation”
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