Abstract
The effects of chronic doses of ozone (O 3 ) and rates of nitrogen (N) fertilizer on N content of ladino clover (Trifolium repens L. cv. Tillman) and tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31), and on N fixation by the clover were studied during the 1979 growing season. Plants of the two species were grown (i) in pots separately, (ii) together in open-top field chambers, and (iii) in ambient air plots. Mean 7 h/day (0930–1630 h eastern daylight time) O 3 concentrations for the study period were 0.03 ppm in charcoal-filtered air chambers, 0.05 ppm in nonfiltered air chambers, 0.08 ppm in nonfiltered air chambers with O 3 added for 7 h/day, and 0.05 ppm in ambient air. Shoot N concentrations (milligrams per gram dry weight) for clover and fescue were not modified by O 3 exposures nor by N fertilization. Higher ozone levels led to reduced system N fixation (milligrams N per pot) by clover grown separately or together with fescue. Nitrogen fixation by ladino clover grown with tall fescue was 1.4 times greater than that by the clover grown alone. Nitrogen fixation by clover as estimated by the difference method was approximately 45% lower than N fixation as estimated by the 15 N dilution method. Nitrogen fixation estimated by the difference method declined significantly with increasing N fertilization. This was not the case for N fixation estimated by the 15 N dilution method.
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Claims 9
Claim · model-written summary
Shoot N concentrations of ladino clover were not modified by O3 exposures.
- Taxon
- ladino clovere0
- Material
- cv. Tillmane0
- Treatment
- O3 exposurese1
- Outcome
- Shoot N concentrationse1
- Direction
- not modifiede1
Not reportedComparator
Verbatim
e0“ladino clover (Trifolium repens L. cv. Tillman)”
e1“Shoot N concentrations (milligrams per gram dry weight) for clover and fescue were not modified by O3 exposures nor by N fertilization”
Claim · model-written summary
Shoot N concentrations of tall fescue were not modified by O3 exposures.
- Taxon
- tall fescue
Lolium arundinaceume7 - Material
- cv. Kentucky 31e7
- Treatment
- O3 exposurese1
- Outcome
- Shoot N concentrationse1
- Direction
- not modifiede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31)”
e1“Shoot N concentrations (milligrams per gram dry weight) for clover and fescue were not modified by O3 exposures nor by N fertilization”
Claim · model-written summary
Shoot N concentrations of ladino clover were not modified by N fertilization.
- Taxon
- ladino clovere0
- Material
- cv. Tillmane0
- Treatment
- N fertilizatione1
- Outcome
- Shoot N concentrationse1
- Direction
- not modifiede1
Not reportedComparator
Verbatim
e0“ladino clover (Trifolium repens L. cv. Tillman)”
e1“Shoot N concentrations (milligrams per gram dry weight) for clover and fescue were not modified by O3 exposures nor by N fertilization”
Claim · model-written summary
Shoot N concentrations of tall fescue were not modified by N fertilization.
- Taxon
- tall fescueLolium arundinaceume7
- Material
- cv. Kentucky 31e7
- Treatment
- N fertilizatione1
- Outcome
- Shoot N concentrationse1
- Direction
- not modifiede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31)”
e1“Shoot N concentrations (milligrams per gram dry weight) for clover and fescue were not modified by O3 exposures nor by N fertilization”
Claim · model-written summary
Higher ozone levels reduced system N fixation by clover grown separately or together with fescue.
- Taxon
- ladino clovere0
- Treatment
- Higher ozone levelse2
- Outcome
- system N fixatione2
- Direction
- reducede2
- Qualifier
- grown separately or together with fescuee2
Not reportedComparator
Verbatim
e0“ladino clover (Trifolium repens L. cv. Tillman)”
e2“Higher ozone levels led to reduced system N fixation (milligrams N per pot) by clover grown separately or together with fescue”
Claim · model-written summary
Nitrogen fixation by ladino clover grown with tall fescue was 1.4 times greater than by clover grown alone.
Verbatim
e3“Nitrogen fixation by ladino clover grown with tall fescue was 1.4 times greater than that by the clover grown alone”
Claim · model-written summary
Nitrogen fixation estimated by the difference method was approximately 45% lower than by the 15N dilution method.
- Outcome
- Nitrogen fixation by clover as estimated by the difference methode4
- Direction
- lowere4
- Value
- approximately 45%e4
- Comparator
- N fixation as estimated by the 15 N dilution methode4
TrifoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Nitrogen fixation by clover as estimated by the difference method was approximately 45% lower than N fixation as estimated by the 15 N dilution method”
Claim · model-written summary
Nitrogen fixation estimated by the difference method declined significantly with increasing N fertilization.
Verbatim
e0“ladino clover (Trifolium repens L. cv. Tillman)”
e5“Nitrogen fixation estimated by the difference method declined significantly with increasing N fertilization”
Claim · model-written summary
Nitrogen fixation estimated by the 15N dilution method did not decline with increasing N fertilization.
Verbatim
e0“ladino clover (Trifolium repens L. cv. Tillman)”
e1“Nitrogen fixation estimated by the difference method declined significantly with increasing N fertilization. This was not the case for N fixation estimated by the 15 N dilution method”
The same questions in other papers
fertilization · nutrient: content · Lolium arundinaceum (tall fescue)Positive and negative results
6 papers in the same direction as this paper · 20 in the opposite direction
- positive
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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.