Abstract
There has recently been concern in Brazil whether biological N 2 fixation (BNF) is capable of meeting the increased N needs of newly released more productive cultivars, as well as doubts about the advantages of annual reinoculation of seeds. Forty experiments were performed over 3 yr in oxisols containing at least 103 cells of Bradyrhizobium g -1 in the State of Paraná, southern Brazil to estimate the contributions of BNF and of N fertilizer. The experiments were performed at two sites, Londrina and Ponta Grossa, under conventional (CT) or no-tillage (NT) systems, with two cultivars [Embrapa 48 (early-maturing) or BRS 134 (medium-maturity group)]. Treatments included non-inoculated controls without or with 200 kg of N ha -1 , and inoculation without or with N fertilizer applied at sowing (30 kg of N ha -1 ), or at the R2 or R4 stage (50 kg of N ha -1 ). Compared with the non-inoculated control, reinoculation significantly increased the contribution of BNF estimated by the N-ureide technique (on average from 79 to 84%), grain yield (on average 127 kg ha -1 , or 4.7%) and total N in grains (on average 6.6%). The application of 200 kg of N fertilizer ha -1 drastically decreased nodulation and the contribution of BNF (to 44%), with no further gains in yield. Application of starter N at sowing decreased nodulation and the contribution of BNF slightly and did not increase yields, while N fertilizer at R2 and R4 stages decreased the contribution of BNF (to 77%) and also yields. Estimates of volatilization of ammonia ranged from 15 to 25% of the N fertilizer applied, and no residual benefits of the N fertilizer in the winter crop were observed. The results highlight the economical and environmental benefits resulting from replacing N fertilizer with inoculation in Brazil, and reinforce the benefits of reinoculation, even in soils with high populations of Bradyrhizobium. Key words: Biological nitrogen fixation, Bradyrhizobium, inoculation, N fertilizers, ureides, soybean
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Claims 13
Claim · model-written summary
Reinoculation raised the estimated biological nitrogen fixation contribution from 79% to 84%.
- Taxon
- soybean
Glycine maxt0 - Treatment
- reinoculatione0
- Interactor
- Bradyrhizobium
Bradyrhizobiume1symbiont - Outcome
- contribution of BNFe0
- Direction
- increasede0
- Value
- 79 to 84%e0
- Comparator
- non-inoculated controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with the non-inoculated control, reinoculation significantly increased the contribution of BNF estimated by the N-ureide technique (on average from 79 to 84%)”
t0“soybean”
e1“cells of Bradyrhizobium g -1”
Claim · model-written summary
Reinoculation increased grain yield by an average 127 kg ha -1 or 4.7%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- reinoculatione0
- Interactor
- BradyrhizobiumBradyrhizobiume1symbiont
- Outcome
- grain yielde0
- Direction
- increasede0
- Value
- 127 kg ha -1e0
- Qualifier
- 4.7%e0
- Comparator
- non-inoculated controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with the non-inoculated control, reinoculation significantly increased the contribution of BNF estimated by the N-ureide technique (on average from 79 to 84%), grain yield (on average 127 kg ha -1 , or 4.7%)”
t0“soybean”
e1“cells of Bradyrhizobium g -1”
Claim · model-written summary
Reinoculation increased total grain nitrogen by an average 6.6%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- reinoculatione0
- Interactor
- BradyrhizobiumBradyrhizobiume1symbiont
- Outcome
- total N in grainse0
- Direction
- increasede0
- Value
- 6.6%e0
- Comparator
- non-inoculated controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared with the non-inoculated control, reinoculation significantly increased the contribution of BNF estimated by the N-ureide technique (on average from 79 to 84%), grain yield (on average 127 kg ha -1 , or 4.7%) and total N in grains (on average 6.6%).”
t0“soybean”
e1“cells of Bradyrhizobium g -1”
Claim · model-written summary
Applying 200 kg of nitrogen fertilizer per hectare drastically decreased nodulation and BNF contribution to 44%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- 200 kg of N fertilizer ha -1e0
- Outcome
- nodulation and the contribution of BNFe0
- Direction
- decreasede0
- Value
- 44%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The application of 200 kg of N fertilizer ha -1 drastically decreased nodulation and the contribution of BNF (to 44%), with no further gains in yield.”
t0“soybean”
Claim · model-written summary
Applying 200 kg nitrogen fertilizer per hectare gave no further yield gain.
- Taxon
- soybeanGlycine maxt0
- Treatment
- 200 kg of N fertilizer ha -1e0
- Outcome
- yielde0
- Direction
- no further gainse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The application of 200 kg of N fertilizer ha -1 drastically decreased nodulation and the contribution of BNF (to 44%), with no further gains in yield.”
t0“soybean”
Claim · model-written summary
Starter nitrogen at sowing slightly decreased nodulation and BNF contribution.
- Taxon
- soybeanGlycine maxt0
- Treatment
- starter N at sowinge0
- Outcome
- nodulation and the contribution of BNFe0
- Direction
- decreasede0
- Qualifier
- slightlye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of starter N at sowing decreased nodulation and the contribution of BNF slightly and did not increase yields”
t0“soybean”
Claim · model-written summary
Starter nitrogen at sowing did not increase yield.
- Taxon
- soybeanGlycine maxt0
- Treatment
- starter N at sowinge0
- Outcome
- yieldse0
- Direction
- did not increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of starter N at sowing decreased nodulation and the contribution of BNF slightly and did not increase yields”
t0“soybean”
Claim · model-written summary
Nitrogen applied at R2 and R4 decreased BNF contribution to 77%.
- Taxon
- soybeanGlycine maxt0
- Treatment
- N fertilizer at R2 and R4 stagese0
- Outcome
- contribution of BNFe0
- Direction
- decreasede0
- Value
- 77%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N fertilizer at R2 and R4 stages decreased the contribution of BNF (to 77%) and also yields.”
t0“soybean”
Claim · model-written summary
Nitrogen applied at R2 and R4 also decreased yield.
- Taxon
- soybeanGlycine maxt0
- Treatment
- N fertilizer at R2 and R4 stagese0
- Outcome
- yieldse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N fertilizer at R2 and R4 stages decreased the contribution of BNF (to 77%) and also yields.”
t0“soybean”
Claim · model-written summary
Estimated ammonia volatilization was 15–25% of applied nitrogen fertilizer.
- Taxon
- soybeanGlycine maxt0
- Outcome
- volatilization of ammoniae0
- Value
- 15 to 25%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Estimates of volatilization of ammonia ranged from 15 to 25% of the N fertilizer applied”
t0“soybean”
Claim · model-written summary
Nitrogen fertilizer showed no residual benefits in the winter crop.
- Taxon
- soybeanGlycine maxt0
- Treatment
- N fertilizere0
- Outcome
- residual benefitse0
- Direction
- no residual benefitse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no residual benefits of the N fertilizer in the winter crop were observed”
t0“soybean”
Claim · model-written summary
The authors conclude replacing nitrogen fertilizer with inoculation has economic and environmental benefits in Brazil.
- Taxon
- soybeanGlycine maxt0
- Outcome
- replacing N fertilizer with inoculatione0
- Setting
- Brazile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The results highlight the economical and environmental benefits resulting from replacing N fertilizer with inoculation in Brazil”
t0“soybean”
Claim · model-written summary
The authors support reinoculation even in soils with high Bradyrhizobium populations.
- Taxon
- soybeanGlycine maxt0
- Interactor
- BradyrhizobiumBradyrhizobiume0symbiont
- Outcome
- reinoculatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reinforce the benefits of reinoculation, even in soils with high populations of Bradyrhizobium”
t0“soybean”
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