Abstract
Core Ideas Compost‐based management enhanced soil organic matter in a Michigan Alfisol. Nitrogen fixation rates in soybean and red clover varied with management history. Weather markedly influenced the quantity of N fixed in three crop systems. Soil labile pool influence on N fixation can act as an internal regulator. Biological nitrogen fixation (BNF) is a fundamental process relied on in agriculture, yet few field studies have examined regulation through soil inorganic N feedbacks or considered seasonal effects. In a Michigan long‐term field experiment we examined soil labile C and N pools and impact on BNF in two species, over multiple years. The 15 N natural abundance method was used to quantify BNF, with nodulated and non‐nodulated soybean [ Glycine max (L.) Merr.] isolines and red clover ( Trifolium pratense L.). Soil organic C status of plots was consistent with a gradient established through historical inputs: 0.8% (fertilizer management) to 0.9% (+ cover crop) to 1.2% (+ compost + cover crop). The fraction of nitrogen derived from atmosphere (fNdfa) in red clover and soybean over 3 yr was 61 to 58% with compost management, and 71 to 72% with fertilizer. This represented a downregulation of 19% (red clover) and 15% (soybean) in compost and cover crop managed plots, relative to inorganic fertilizer. In addition to management effects, we found that weather markedly influenced the total amount of N fixation over the 3 yr of the study. A mesic season supported vigorous soybean growth and 195 kg N ha −1 BNF, compared to 95 and 90 kg N ha −1 BNF in a dry and an excessively wet season. This study found that compost‐based management increased pools of labile C and N that internally downregulated BNF, while enhancing soybean yield compared to conventional management.
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Claims 7
Claim · model-written summary
Historical compost and cover crop inputs increased soil organic carbon to 1.2% versus 0.8% under fertilizer management.
- Treatment
- + compost + cover crope0
- Outcome
- Soil organic C statuse0
- Direction
- increaseinferrede0
- Value
- 1.2%e0
- Qualifier
- 0.8%e0
- Comparator
- fertilizer managemente0
Not reportedTaxon
Verbatim
e0“Soil organic C status of plots was consistent with a gradient established through historical inputs: 0.8% (fertilizer management) to 0.9% (+ cover crop) to 1.2% (+ compost + cover crop)”
Claim · model-written summary
Compost management reduced the red clover atmospheric nitrogen fraction by 19% relative to inorganic fertilizer.
- Taxon
- red clover
Trifolium pratensee0 - Treatment
- compost and cover crop managed plotse0
- Outcome
- downregulatione0
- Direction
- downregulatione0
- Value
- 19%e0
- Comparator
- inorganic fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This represented a downregulation of 19% (red clover) and 15% (soybean) in compost and cover crop managed plots, relative to inorganic fertilizer”
Claim · model-written summary
Compost management reduced the soybean atmospheric nitrogen fraction by 15% relative to inorganic fertilizer.
- Taxon
- soybean
Glycine maxe0 - Treatment
- compost and cover crop managed plotse0
- Outcome
- downregulatione0
- Direction
- downregulatione0
- Value
- 15%e0
- Comparator
- inorganic fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This represented a downregulation of 19% (red clover) and 15% (soybean) in compost and cover crop managed plots, relative to inorganic fertilizer”
Claim · model-written summary
Weather markedly influenced nitrogen fixation across three years.
Not reportedTaxonSettingDirection
Verbatim
e0“weather markedly influenced the total amount of N fixation over the 3 yr of the study”
Claim · model-written summary
A mesic season supported 195 kg N ha −1 soybean nitrogen fixation, versus 95 in a dry season and 90 in an excessively wet season.
- Taxon
- soybeanGlycine maxe0
- Outcome
- BNFe0
- Direction
- higherinferrede0
- Value
- 195 kg N ha −1e0
- Qualifier
- 95 and 90 kg N ha −1 BNFe0
- Comparator
- a dry and an excessively wet seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A mesic season supported vigorous soybean growth and 195 kg N ha −1 BNF, compared to 95 and 90 kg N ha −1 BNF in a dry and an excessively wet season”
Claim · model-written summary
Compost management enhanced soybean yield compared with conventional management.
- Taxon
- soybeanGlycine maxe0
- Treatment
- compost‐based managemente0
- Outcome
- soybean yielde0
- Direction
- enhancinge0
- Comparator
- conventional managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compost‐based management increased pools of labile C and N that internally downregulated BNF, while enhancing soybean yield compared to conventional management”
Claim · model-written summary
Compost management increased labile C and N pools that downregulated nitrogen fixation.
Not reportedTaxon
Verbatim
e0“compost‐based management increased pools of labile C and N that internally downregulated BNF”
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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.