Abstract
It has been well known that elevated atmospheric CO2 concentration can not only promote crops soil nitrogen uptake directly through increasing plant photosynthesis and aboveground biomass, but also influence the soil nitrogen and carbon status, indirectly through enhancing root biomass, changing root activity, root exudates and root spatial distribution. However, the effects of elevated atmospheric CO2 concentration on soil nitrogen cycle at rhizosphere and non-rhizosphere, especially under different soil fertilized nitrogen conditions, were unclear. This study aimed to reveal the effects of elevated atmospheric CO2 concentrations on the contents of soil inorganic nitrogen(nitrateN, ammonium-N)and organic nitrogen at rhizosphere and non-rhizosphere after crop harvest and under different nitrogen fertilizer applications for a wheat and rice rotation. The FACE (Free air carbon dioxide enrichment)systems, built at Xiaoji Town, Jiangdu City, Jiangsu Province(119°42′ 0″ E, 32°35′5″ N), provided in field two levels of CO2 concentration:ambien(t370 μmol·mol-1, as control)and elevated (370+200)μmol·mol-1, with three repeats. For each CO2 concentration level there existed two nitrogen fertilizer application rates:low(125 and 112. 5 kg·hm-2, LN)and conventional (250 and 225 kg·hm-2, NN)for rice season of 2005 and for wheat season of 2004—2005, respectively. The results showed that, while significantly increased crop biomass both in rice and wheat compared with ambient CO2, elevated CO2 decreased soil nitrate-N for rice significantly, especially at NN, but no pronounced change in soil nitrate-N was found for wheat. And elevated CO2 affected soil nitrate-N at root rhizosphere more greatly than that at non-rhizosphere. There were no significant effects of elevated CO2 on soil ammonium-N for both rice and wheat, although with a slight rise trend with CO2 elevated for rice and a declined trend, especially at rhizosphere, for wheat. With nitrogen application rate increased, soil ammonium-N content was increased more at ambient CO2 than at elevated CO2. We observed no significant increase in soil organic nitrogen under elevated CO2 compared with ambient CO2 and, founded more organic nitrogen in wheat season was input into soil than in rice season, and for wheat season, more organic nitrogen would amass in rhizosphere than in non-rhizosphere with more nitrogen applied.
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Claims 11
Claim · model-written summary
Elevated CO2 significantly increased rice biomass.
- Taxon
- rice
Oryza sativae0 - Treatment
- CO2e0
- Outcome
- crop biomasse0
- Direction
- increasede0
- Comparator
- ambient CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while significantly increased crop biomass both in rice and wheat compared with ambient CO2”
Claim · model-written summary
Elevated CO2 significantly increased wheat biomass.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- CO2e0
- Outcome
- crop biomasse0
- Direction
- increasede0
- Comparator
- ambient CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while significantly increased crop biomass both in rice and wheat compared with ambient CO2”
Claim · model-written summary
Elevated CO2 significantly decreased soil nitrate-N in rice, especially with conventional nitrogen.
- Taxon
- riceOryza sativae0
- Treatment
- elevated CO2e0
- Outcome
- soil nitrate-Ne0
- Direction
- decreasede0
- Qualifier
- especially at NNe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO2 decreased soil nitrate-N for rice significantly, especially at NN”
Claim · model-written summary
Elevated CO2 did not pronouncedly change soil nitrate-N in wheat.
- Taxon
- wheatTriticum aestivume0
- Treatment
- elevated CO2e0
- Outcome
- soil nitrate-Ne0
- Direction
- no pronounced changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO2 decreased soil nitrate-N for rice significantly, especially at NN, but no pronounced change in soil nitrate-N was found for wheat”
Claim · model-written summary
Elevated CO2 affected rhizosphere soil nitrate-N more than non-rhizosphere soil nitrate-N.
Verbatim
e0“elevated CO2 affected soil nitrate-N at root rhizosphere more greatly than that at non-rhizosphere”
t0“Crops”
Claim · model-written summary
Elevated CO2 had no significant effect on soil ammonium-N in rice, despite a slight rise trend.
- Taxon
- riceOryza sativae0
- Treatment
- elevated CO2e0
- Outcome
- soil ammonium-Ne0
- Direction
- slight risee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were no significant effects of elevated CO2 on soil ammonium-N for both rice and wheat, although with a slight rise trend with CO2 elevated for rice”
Claim · model-written summary
Elevated CO2 had no significant effect on soil ammonium-N in wheat, despite a declining trend.
- Taxon
- wheatTriticum aestivume0
- Treatment
- elevated CO2e0
- Outcome
- soil ammonium-Ne0
- Direction
- declinede0
- Qualifier
- especially at rhizospheree0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were no significant effects of elevated CO2 on soil ammonium-N for both rice and wheat, although with a slight rise trend with CO2 elevated for rice and a declined trend, especially at rhizosphere, for wheat”
Claim · model-written summary
Increasing nitrogen application raised soil ammonium-N more under ambient than elevated CO2.
Verbatim
e0“With nitrogen application rate increased, soil ammonium-N content was increased more at ambient CO2 than at elevated CO2”
t0“Crops”
Claim · model-written summary
Elevated CO2 did not significantly increase soil organic nitrogen.
Verbatim
e0“no significant increase in soil organic nitrogen under elevated CO2 compared with ambient CO2”
t0“Crops”
Claim · model-written summary
More organic nitrogen was input into soil in the wheat season than rice season.
- Taxon
- wheatTriticum aestivume0
- Outcome
- organic nitrogen in wheat season was input into soile0
- Direction
- moree0
- Comparator
- rice seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“more organic nitrogen in wheat season was input into soil than in rice season”
Claim · model-written summary
With more nitrogen applied in wheat, more organic nitrogen accumulated in the rhizosphere than the non-rhizosphere.
- Taxon
- wheatTriticum aestivume0
- Treatment
- more nitrogen appliede0
- Outcome
- organic nitrogene0
- Direction
- moree0
- Comparator
- non-rhizospheree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for wheat season, more organic nitrogen would amass in rhizosphere than in non-rhizosphere with more nitrogen applied”
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See all 145 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.