Abstract
One major reason legumes are utilized in farming systems is for their ability to maintain the soil nitrogen balance when incorporated into crop rotations.As such legumes can play an important role in both maintaining and improving crop yields.It is therefore important to quantify the total amount of nitrogen fixated through the biological nitrogen fixation(BNF) process used by legumes and to determine how much of this fixated N is available to the following crop.In doing so,this will enable greater precision in terms of appropriate fertilizer application rates and can increase fertilizer use efficiency.In 2002 and 2003,the()~(15)N natural abundance technique was used to record the percentage of biological nitrogen fixation(%Ndfa) fixated by soybeans and the soybeans N contribution to a spring maize-winter wheat-summer soybean rotation system.The field experiment which was located in the Gansu Loess Plateau used four tillage treatments.These were: conventional tillage(T),conventional tillage with stubble retention (TS),no-tillage(NT),and no-tillage with stubble retention(NTS).In general the %Ndfa by soybean was higher in 2003 than in 2002,related to 2003 receiving a significantly more rainfall.The %Ndfa by soybean in the TS treatment was significantly higher than in the other three treatments.The TS treatment benefited from a higher N fixing enzyme activity which improved the soybeans BNF ability and as a consequence resulted in a higher yield.A negative relationship between the amount of N fixed by soybean and the amount of NO_3-N in the 0-30cm soil profiles was found.A soil NO_3-N concentration of 40 kgN/hm~2 was thought to be the critical value above which BNF activity was reduced.Soybean obtained its N requirements from both soil N and BNF.When there was no BNF activity recorded,N was supplied wholly by soil N,which led to soil N depletion and soil N scarcity.The aboveground biomass of soybeans increased with increases in %Ndfa,however this finding was most evident in the TS treatment.A positive relationship between the amount of N fixed by soybean and its above-ground biomass was also found.In 2002,the treatment effects on the proportion of soybean BNF to total N input ranged from 13～22%,with the highest proportion recorded under the TS treatment. In 2003,the %Ndfa ranged from 43.8 %～ 62.4%,with the amount of fixated N ranging from 10.7～17.6kgN/hm~2 and the proportion total N contributed by N fixation ranging from 40%～63%.
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Claims 16
Claim · model-written summary
Soybean nitrogen fixation percentage was higher in 2003 than 2002.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the %Ndfa by soybean was higher in 2003 than in 2002”
Claim · model-written summary
TS produced a significantly higher soybean nitrogen fixation percentage than the other three tillage treatments.
- Taxon
- soybean
Glycine maxe0 - Treatment
- TS treatmente0
- Outcome
- %Ndfae0
- Direction
- highere0
- Comparator
- other three treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The %Ndfa by soybean in the TS treatment was significantly higher than in the other three treatments.”
Claim · model-written summary
TS increased nitrogen fixing enzyme activity.
- Taxon
- soybeanGlycine maxt0
- Treatment
- TS treatmente0
- Outcome
- N fixing enzyme activitye0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The TS treatment benefited from a higher N fixing enzyme activity”
t0“biological N fixation ability of soybean”
Claim · model-written summary
TS improved soybean BNF ability.
- Taxon
- soybeansGlycine maxe0
- Treatment
- TS treatmente0
- Outcome
- BNF abilitye0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The TS treatment benefited from a higher N fixing enzyme activity which improved the soybeans BNF ability”
Claim · model-written summary
TS resulted in higher soybean yield.
- Taxon
- soybeansGlycine maxe0
- Treatment
- TS treatmente0
- Outcome
- yielde0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The TS treatment benefited from a higher N fixing enzyme activity which improved the soybeans BNF ability and as a consequence resulted in a higher yield.”
Claim · model-written summary
Fixed soybean nitrogen was negatively related to soil nitrate nitrogen.
- Taxon
- soybeanGlycine maxe0
- Compound
- NO_3-Ne0
- Outcome
- amount of N fixed by soybeane0
- Direction
- negativee0
- Qualifier
- 0-30cm soil profilese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A negative relationship between the amount of N fixed by soybean and the amount of NO_3-N in the 0-30cm soil profiles was found.”
Claim · model-written summary
BNF activity was reduced above a soil nitrate concentration of 40 kgN/hm~2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A soil NO_3-N concentration of 40 kgN/hm~2 was thought to be the critical value above which BNF activity was reduced.”
t0“biological N fixation ability of soybean”
Claim · model-written summary
Without BNF, soil supplied all soybean nitrogen requirements.
- Taxon
- soybeanGlycine maxt0
- Outcome
- N was supplied wholly by soil Ne0
- Qualifier
- no BNF activitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When there was no BNF activity recorded,N was supplied wholly by soil N”
t0“biological N fixation ability of soybean”
Claim · model-written summary
Absence of BNF led to soil nitrogen depletion and scarcity.
- Taxon
- soybeanGlycine maxt0
- Outcome
- soil N depletion and soil N scarcitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which led to soil N depletion and soil N scarcity.”
t0“biological N fixation ability of soybean”
Claim · model-written summary
Soybean aboveground biomass increased with nitrogen fixation percentage, especially under TS.
- Taxon
- soybeansGlycine maxe0
- Treatment
- TS treatmente0
- Outcome
- aboveground biomasse0
- Direction
- increasede0
- Qualifier
- %Ndfae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The aboveground biomass of soybeans increased with increases in %Ndfa,however this finding was most evident in the TS treatment.”
Claim · model-written summary
Fixed soybean nitrogen was positively related to aboveground biomass.
- Taxon
- soybeanGlycine maxe0
- Organ / stage
- above-ground biomasse0
- Outcome
- amount of N fixed by soybeane0
- Direction
- positivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A positive relationship between the amount of N fixed by soybean and its above-ground biomass was also found.”
Claim · model-written summary
In 2002, soybean BNF contributed 13～22% of total nitrogen input across treatments.
- Taxon
- soybeanGlycine maxe0
- Outcome
- proportion of soybean BNF to total N inpute0
- Value
- 13～22%e0
- Setting
- 2002e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 2002,the treatment effects on the proportion of soybean BNF to total N input ranged from 13～22%”
Claim · model-written summary
TS had the highest 2002 BNF contribution to total nitrogen input.
- Taxon
- soybeanGlycine maxt0
- Treatment
- TS treatmente0
- Outcome
- proportione0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with the highest proportion recorded under the TS treatment.”
t0“biological N fixation ability of soybean”
Claim · model-written summary
In 2003, soybean nitrogen fixation percentage ranged from 43.8% to 62.4%.
- Taxon
- soybeanGlycine maxt0
- Outcome
- %Ndfae0
- Value
- 43.8 %～ 62.4%e0
- Setting
- 2003e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 2003,the %Ndfa ranged from 43.8 %～ 62.4%”
t0“biological N fixation ability of soybean”
Claim · model-written summary
In 2003, soybean fixed nitrogen ranged from 10.7 to 17.6 kgN/hm~2.
- Taxon
- soybeanGlycine maxt0
- Outcome
- amount of fixated Ne0
- Value
- 10.7～17.6kgN/hm~2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with the amount of fixated N ranging from 10.7～17.6kgN/hm~2”
t0“biological N fixation ability of soybean”
Claim · model-written summary
In 2003, fixation contributed 40% to 63% of total nitrogen.
- Taxon
- soybeanGlycine maxt0
- Outcome
- proportion total N contributed by N fixatione0
- Value
- 40%～63%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the proportion total N contributed by N fixation ranging from 40%～63%.”
t0“biological N fixation ability of soybean”
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