Abstract
Soil organic carbon (SOC) is sensitive to management of tillage, residue (stover) harvest, and N fertilization in corn ( Zea mays L.), but little is known about associated root biomass including rhizodeposition. Natural C isotope abundance (δ 13 C) and total C content, measured in paired plots of stover harvest and return were used to estimate corn‐derived SOC (cdSOC) and the contribution of nonharvestable biomass (crown, roots, and rhizodeposits) to the SOC pool. Rhizodeposition was estimated for each treatment in a factorial of three tillage treatments (moldboard, MB; chisel, CH; and no‐till, NT), two N fertilizer rates (200 and 0 kg N ha −1 ), and two corn residue managements. Treatments influenced cdSOC across a wide range (6.8–17.8 Mg C ha −1 ). Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha −1 , and increased rhizodeposition by at least 110% compared with that with no N fertilizer. Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC. The amount of stover source carbon ( S SC) responded to tillage (MB > CH > NT), but tillage affected the amount of cdSOC differently (NT > CH > MB). Total SOC was maintained only by both N fertilization and stover return during the 13‐yr period. The ratio of SC in the nonharvestable biomass to S SC ranged from 1.01 to 3.49; a ratio of 0.6 conforms to a root‐to‐shoot ratio of 0.4 when the root biomass includes 50% rhizodeposits. Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH), even though N fertilization, stover harvest, and tillage all significantly influenced SC. Decomposition of labile rhizodeposits was a major component of the nonhumified fraction. Rhizodeposition was as much as three times greater than suggested by laboratory and other controlled studies. To understand and manage the entire C cycle, roots and rhizodeposition must be included in the analysis at the field level.
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Claims 18
Claim · model-written summary
Management treatments changed corn-derived soil organic carbon across 6.8–17.8 Mg C ha −1.
- Taxon
- corn
Zea mays subsp. mayse1 - Outcome
- corn‐derived SOCe2
- Value
- 6.8–17.8 Mg C ha −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Treatments influenced cdSOC across a wide range (6.8–17.8 Mg C ha −1 ).”
e1“corn ( Zea mays L.)”
e2“corn‐derived SOC (cdSOC)”
Claim · model-written summary
N fertilization increased stover C by 20%.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Nitrogen fertilizatione0
- Outcome
- stover Ce0
- Direction
- increasede0
- Value
- 20%e0
- Comparator
- no N fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha −1 , and increased rhizodeposition by at least 110% compared with that with no N fertilizer.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
N fertilization increased corn-derived SOC by 1.9 Mg C ha −1.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Nitrogen fertilizatione0
- Outcome
- cdSOCe0
- Direction
- increasede0
- Value
- 1.9 Mg C ha −1e0
- Comparator
- no N fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha −1 , and increased rhizodeposition by at least 110% compared with that with no N fertilizer.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
N fertilization increased rhizodeposition by at least 110%.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Nitrogen fertilizatione0
- Outcome
- rhizodepositione0
- Direction
- increasede0
- Value
- at least 110%e0
- Comparator
- no N fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha −1 , and increased rhizodeposition by at least 110% compared with that with no N fertilizer.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Stover harvest reduced total source carbon by 20%.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Stover harveste0
- Outcome
- total source carbon (SC)e0
- Direction
- reducede0
- Value
- 20%e0
- Comparator
- stover returne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Stover harvest reduced corn-derived SOC by 35%.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Stover harveste0
- Outcome
- cdSOCe0
- Direction
- reducede0
- Value
- 35%e0
- Comparator
- stover returne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Stover harvest reduced total soil organic carbon.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- Stover harveste0
- Outcome
- total SOCe0
- Direction
- reducede0
- Comparator
- stover returne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Stover source carbon ranked moldboard greater than chisel greater than no-till.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- tillagee0
- Outcome
- stover source carbone0
- Direction
- MB > CH > NTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The amount of stover source carbon ( S SC) responded to tillage (MB > CH > NT)”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Corn-derived SOC ranked no-till greater than chisel greater than moldboard.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- tillagee0
- Outcome
- cdSOCe0
- Direction
- NT > CH > MBe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tillage affected the amount of cdSOC differently (NT > CH > MB)”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Total SOC was maintained over 13 years only with N fertilization and stover return together.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- both N fertilization and stover returne0
- Outcome
- Total SOCe0
- Direction
- maintainede0
- Qualifier
- during the 13‐yr periode0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total SOC was maintained only by both N fertilization and stover return during the 13‐yr period.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Nonharvestable biomass source C to stover source C ratio ranged 1.01 to 3.49.
- Taxon
- cornZea mays subsp. mayse1
- Outcome
- ratio of SC in the nonharvestable biomass to S SCe0
- Value
- 1.01 to 3.49e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ratio of SC in the nonharvestable biomass to S SC ranged from 1.01 to 3.49”
e1“corn ( Zea mays L.)”
Claim · model-written summary
A 0.6 source C ratio corresponds to a 0.4 root-to-shoot ratio with 50% rhizodeposits.
- Taxon
- cornZea mays subsp. mayse1
- Outcome
- root‐to‐shoot ratioe0
- Value
- 0.4e0
- Qualifier
- root biomass includes 50% rhizodepositse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a ratio of 0.6 conforms to a root‐to‐shoot ratio of 0.4 when the root biomass includes 50% rhizodeposits”
e1“corn ( Zea mays L.)”
Claim · model-written summary
No-till retained 0.26 of source C as corn-derived SOC.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- NTe0
- Outcome
- fraction of SC retained as cdSOCe0
- Value
- 0.26e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH)”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Moldboard tillage retained 0.11 of source C as corn-derived SOC.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- MBe0
- Outcome
- fraction of SC retained as cdSOCe0
- Value
- 0.11e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH)”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Chisel tillage retained 0.11 of source C as corn-derived SOC.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- CHe0
- Outcome
- fraction of SC retained as cdSOCe0
- Value
- 0.11e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH)”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Decomposition of labile rhizodeposits contributed substantially to the nonhumified fraction.
- Taxon
- cornZea mays subsp. mayse1
- Outcome
- nonhumified fractione0
- Qualifier
- Decomposition of labile rhizodepositse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decomposition of labile rhizodeposits was a major component of the nonhumified fraction.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Rhizodeposition was up to three times greater than laboratory and controlled-study estimates.
- Taxon
- cornZea mays subsp. mayse1
- Outcome
- Rhizodepositione0
- Direction
- greatere0
- Value
- three timese0
- Comparator
- laboratory and other controlled studiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rhizodeposition was as much as three times greater than suggested by laboratory and other controlled studies.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
The authors recommend including roots and rhizodeposition in field C-cycle analysis.
- Taxon
- cornZea mays subsp. mayse1
- Outcome
- roots and rhizodeposition must be included in the analysis at the field levele0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To understand and manage the entire C cycle, roots and rhizodeposition must be included in the analysis at the field level.”
e1“corn ( Zea mays L.)”
The same questions in other papers
fertilization · soil: chemistry · Zea mays (maize)Positive and negative results
302 papers in the same direction as this paper · 34 in the opposite direction · 2 reporting no difference from an alternative
- negative
- no effect
- no effect
335 papers more in this group
See all 339 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.